{"1": {"fulltext": "", "height": "4672", "width": "2877", "jp2-path": "dynamoelectricma01shel_0001.jp2"}, "2": {"fulltext": "", "height": "4554", "width": "2884", "jp2-path": "dynamoelectricma01shel_0002.jp2"}, "3": {"fulltext": "", "height": "4554", "width": "2884", "jp2-path": "dynamoelectricma01shel_0003.jp2"}, "4": {"fulltext": "", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0004.jp2"}, "5": {"fulltext": "", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0005.jp2"}, "6": {"fulltext": "", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0006.jp2"}, "7": {"fulltext": "DYNAMO ELECTRIC MACHINERY;\\nAW\\nITS CONSTRUCTION, DESIGN,\\nAND OPERATION\\nDIRECT CURRENT MACHINES\\nS BY\\nSAMUEL SHELDON, A.M., Ph.D.\\nPROFESSOR OF PHYSICS AND ELECTRICAL ENGINEERING AT THE POLYTECHNIC\\nINSTITUTE OF BROOKLYN, MEMBER OF THE AMERICAN INSTITUTE\\nOF ELECTRICAL ENGINEERS, AND FELLOW OF THE AMERICAN\\nASSOCIATION FOR THE ADVANCEMENT OF SCIENCE\\nASSISTED BY\\nHOBART MASON, B.S.\\nmt+\\nNEW YORK:\\nD. VAN NOSTRAND COMPANY\\n23 Murray and 27 Warren Sts.\\n19OO", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0007.jp2"}, "8": {"fulltext": "51055\\n.553\\nLibrary of Con?\u00c2\u00bb-\u00c2\u00ab\u00c2\u00abs\\n\u00e2\u0080\u00a2yri Cortii ftcctivco\\nSEP 24 1900\\nS\u00c2\u00a3COWP COPY.\\ntMwrari to\\nOfcOM DIVISION,\\nOCT 1 I90U\\nV?\\noc\\nCopyright, 1900, by\\nD. VAN NOSTRAND COMPANY\\nbO oo.\\nA*\\n\\\\J", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0008.jp2"}, "9": {"fulltext": "PREFACE.\\nThis book is intended to be used primarily in connec-\\ntion with instruction on courses of electrical engineering in\\ninstitutions for technical education. It is laid out on the\\nlines of the lectures and the instruction as given in the\\nPolytechnic Institute of Brooklyn. It is intended equally\\nas much for the general reader, who is seriously looking\\nfor information concerning dynamo electrical machinery of\\nthe types discussed, as well as a book of reference for\\nengineers.\\nThe first two chapters are devoted to a brief but logical\\ndiscussion of the electrical and magnetic laws and facts\\nupon which the operation of this class of machinery\\ndepends. Calculus methods have been employed in a few\\nplaces in these chapters, but the results arrived at by use\\nof them are in such a form that they can be utilized by the\\nreader who is unfamiliar with the processes of the calculus.\\nIn the chapter on design it has seemed advisable to\\nexpress the flux density in lines per square centimeter.\\nBoth the square centimeter and the square inch are used\\nin practice. The alteration of the formulas to square inch\\nunits is obviously simple.\\nWe wish to express our thanks to the various manufac-\\nturing companies who have so courteously given informa-\\ntion, and who have kindly loaned electrotypes of their\\napparatus.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0009.jp2"}, "10": {"fulltext": "", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0010.jp2"}, "11": {"fulltext": "CONTENTS.\\nCHAPTER PAGE\\nI. Electrical Laws and Facts i\\nII. Magnetic Laws and Facts 12\\nIII. Armatures 31\\nIV. Field Magnets 67\\nV. Operation of Armatures 77\\nVI. Efficiency of Operation 92\\nVII. Constant Potential Dynamos 103\\nVIII. Constant Current Dynamos 129\\nIX. Motors 161\\nX. Series Motors 185\\nXI. Dynamotors, Motor-Generators, and Boosters 208\\nXII. Management of Machines 218\\nXIII. The Design of Machines 232\\nXIV. Tests 251", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0011.jp2"}, "12": {"fulltext": "", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0012.jp2"}, "13": {"fulltext": "DYNAMO ELECTRIC MACHINERY.\\nCHAPTER I.\\nELECTRICAL LAWS AND FACTS.\\ni. Mechanical Units Force is that which tends to\\nproduce, alter, or destroy motion. The units of force are\\nthe pound and the dyne. The dyne is that force, which\\nacting on one gram for one second, will produce a velocity\\nof one centimeter per second.\\nWork is the production of motion against resistance.\\nThe units of work are the foot-pound and the erg. The\\nfoot-pound is the work done in lifting a body weighing one\\npound one foot vertically. The erg is the work performed\\nby a force of one dyne in moving a body one centimeter\\nin the direction of its acting. The joule is a larger unit\\nmuch used, and is equal to io 7 ergs.\\nEnergy is the capacity to do work. Energy is divided\\nnto Kinetic energy and Potential energy. A body pos-\\nsesses kinetic energy in virtue of its motion, while poten-\\ntial energy is due to the separation or the disarrangement\\nof attracting particles or masses. A wound up spring has\\npotential energy because of the strained positions of the\\nmolecules, while a weight raised to a height has potential\\nenergy because of the separation of its mass from the", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0013.jp2"}, "14": {"fulltext": "2 DYNAMO ELECTRIC MACHINERY.\\nattracting mass of the earth. The potential energy of a\\nbody is measured by the work required to put the body\\ninto its strained condition. Kinetic energy is measured by\\nthe product of the weight into the square of the velocity\\ndivided by twice the acceleration due to gravity, or\\nWv 2\\nKinetic Energy\\nPower is the rate of performance of work. Its units\\nare the horse-power and the watt. A horse-power is 33,000\\nfoot-pounds per minute. A watt is io 7 ergs per second.\\nOne horse-power is equivalent to 746 watts. The number\\nof watts in an electrical circuit carrying a certain number of\\namperes of current under a pressure of a certain number\\nof volts is expressed by the product of the amperes into the\\nvolts. If we let T equal the torque or twisting moment\\nand to equal the angular velocity where n is the\\nnumber of revolutions per minute), then the horse-power\\n60 o)T itmiT\\nM.Jr.\\n33000 33000\\nIn a belt-driven machine the torque in the shaft is equal\\nto the difference in tension of the two sides of the belt\\nmultiplied by the radius of the pulley in feet, hence\\nT={F-F )r.\\n2. Absolute and Practical Units Since distinction\\nmust continually be made between the absolute units and\\nthe practical units, throughout this work the capital letters\\nE, and R will be used for the practical units, the am-\\npere, the volt, and the ohm, respectively, and the lower-\\ncase letters i, e, and r will stand for the absolute (C. G. S.)\\nunits of current, pressure, and resistance respectively.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0014.jp2"}, "15": {"fulltext": "ELECTRICAL LAWS AND FACTS. 3\\nThe absolute unit of current is such that, when flowing\\nthrough a conductor of one centimeter length, which is\\nbent into an arc of one centimeter radius, it will exert a\\nforce of one dyne on a unit magnet pole 10) placed at the\\ncenter.\\nThe absolute unit of difference of potential exists between\\ntwo points when it requires the expenditure of one erg of\\nwork to move a unit quantity of electricity from one point\\nto the other. This unit of quantity is the quantity which,\\nin a second, passes any cross-section of a conductor in\\nwhich a unit current is flowing.\\nThe absolute unit of resistance is offered by a body when\\nit allows a unit current to flow along it between its two\\nterminals, when maintained at a unit difference of potential.\\nCurrent, 1=\\n10\\nE.M.F., E io 8\\nResistance, R 10V.\\nIt is convenient and rational to make a distinction be-\\ntween electromotive force and difference of potential.\\nElectromotive force is produced when a conductor cuts\\nmagnetic lines of force, or when the electrodes of a pri-\\nmary battery are immersed in a solution. But a difference\\nof potential may exist merely because of an electric cur-\\nrent. Between any two points of a conductor carrying a\\ncurrent there is that which would send a current through\\nan auxiliary wire connecting these points, and we call it\\ndifference of potential. If the current in the original con-\\nductor be doubled, the difference of potential between the\\nsame two points will be doubled, showing that this differ-\\nence of potential exists because of the current flowing in", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0015.jp2"}, "16": {"fulltext": "4 DYNAMO ELECTRIC MACHINERY.\\nthe original conductor. The word pressure is used for\\neither difference of potential or for E.M.F. with obvious\\nrelevancy. k\\n3. Ohm s Law Ohm s law is expressed by the for-\\nmula\\n-i\\nwhere is the number of amperes flowing in an undivided\\ncircuit, E the algebraic sum of all the electromotive forces\\nin that circuit, and R the sum of all the resistances in\\nseries in that circuit.\\nThe form of the equation E IR, as applied to a por-\\ntion of a circuit, is much used under the name of Ohm s\\nlaw. In this case, however, E is not E.M.F., but differ-\\nence of potential, as explained in the last article.\\nIf, in a house lighted by electricity, the service maintains\\na constant pressure of 100 volts at the mains where they\\nenter from the street, and no lights be turned on, then at\\nevery lamp socket in the house there will be a pressure of\\n100 volts. If now a lamp be turned on, it will be working\\non less than 100 volts, because of the drop K ox fall of po-\\ntential. If many lamps be turned on, a considerable drop\\nmay occur. The drop is caused by the resistance of the\\nwires carrying the current from the place of constant po-\\ntential to the place where it is used, and the volts lost have\\nbeen consumed in doing useless work in heating the wires.\\nThat the drop is proportional to the current flowing is\\nshown by a simple application of Ohm s law.\\nLet R be the resistance of the line, and E d the volts\\ndrop caused thereby when a current flows. Then\\nE d IR,\\nfrom which it is evident that the drop varies as the cur-\\nrent when the resistance in the line is constant.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0016.jp2"}, "17": {"fulltext": "ELECTRICAL LAWS AND FACTS. 5\\n4. Resistance of Conductors. The resistance R of a con-\\nductor is expressed by the formula R where o- is a\\nconstant called the resistivity, and depending upon the\\nmaterial and the temperature of the conductor, is the\\nlength in centimeters, and A the cross-section in square\\ncms. The reciprocal of the resistivity, is called the con-\\nductivity of a substance.\\nThe conductivity of copper depends on its purity, and on\\nits physical condition, soft copper having 1.0226 times the\\nconductivity of hard copper. Lake copper has a high con-\\nductivity because of its pureness. The same is true of\\nelectrolytic copper. This latter is now very largely used,\\nthough for a while there was a prejudice against it because\\nit was said to be brittle. Temperature affects the resist-\\nance of metals. In pure metals the increase of resistance\\nfor a rise of i\u00c2\u00b0 C. is about .004 times their resistance at\\no\u00c2\u00b0 C. Various alloys of iron, nickel, and manganese have\\na high value for r, and do not have so high a temperature\\ncoefficient as given above. Iron heated in contact with\\n-copper gives a large thermal E.M.F., which militates against\\nits alloys being used for resistances in measuring instru-\\nments.\\nIf in the foregoing expression f or R the centimeter and\\nsquare centimeter be the units of length and cross-section\\nrespectively, then the following list gives the value of o- for\\nvarious metals in microhms (1 microhm Tir w ohm).\\nCopper at o\u00c2\u00b0C, I -594\\nIron\\nSteel\\n18% German Silver\\n30%\\n9-5\\n13.0\\n27.\\n45-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0017.jp2"}, "18": {"fulltext": "6 DYNAMO ELECTRIC MACHINERY.\\nA circular mil is a circle r inch in diameter, and a\\nwire one foot long and one circular mil cross-section is\\ncalled a mil-foot. The resistance of a mil-foot at o\u00c2\u00b0 C. of\\nCopper 9.59 ohms,\\nIron =58. ohms,\\nSteel =82. ohms.\\nThe American Institute of Electrical Engineers has\\nadopted as its standard resistivity for soft copper one given\\nby Matthiessen. A wire of standard soft copper, of uni-\\nform cross-section, of one meter length, and weighing one\\ngram, should have a resistance of o. 141 729 international\\nohms at o\u00c2\u00b0 C. A commercial copper showing this resis-\\ntivity is said to have 100 per cent conductivity. Copper is\\nfrequently found having a conductivity of 102 per cent. It\\nis in these cases almost invariably electrolytic copper.\\n5. Insulating Materials. Materials which are to be\\nused for insulating from each other the various electrical\\ncircuits of dynamo electric machines should possess the\\nfollowing properties\\nThey should have a high insulation resistance, and this\\nresistance should be maintained high over the range of\\ntemperatures to be found in machines. They should\\nfurthermore have a dielectric strength sufficient to pre-\\nclude any possibility of their being perforated by the\\nvoltages liable to exist between the conductors which they\\nseparate. This strength must also exist throughout all\\nprobable ranges of temperature. They must possess such\\nphysical properties as will permit of mechanical manipula-\\ntion, as they must be oftentimes bent and twisted. Of\\ncourse the chemical constitution should not be altered by", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0018.jp2"}, "19": {"fulltext": "ELECTRICAL LAWS AND FACTS. 7\\nany change of temperature to which they would be sub-\\nmitted.\\nMica possesses the highest insulation resistance and the\\nlargest dielectric strength to be found. It requires iooo\\nvolts to perforate a sheet I mil in thickness. Its chemical\\nconstitution is unaffected by high temperatures. It is\\nnot, however, mechanically strong.\\nPreparations of fibrous materials with linseed oil, which,\\nafter being dried, have been thoroughly baked, are fairly\\ngood insulators. As water is generally present in their\\npores, their insulation resistance, upon heating, decreases\\nuntil the temperature has reached ioo\u00c2\u00b0 C, and then it in-\\ncreases. These preparations are mechanically flexible.\\nPreparations of fibrous material with shellac are good in-\\nsulators, but crack upon bending.\\nVulcanized fibers are made by treating paper fiber chemi-\\ncally, and, when dried, they have a fairly high insulation\\nresistance, but they readily absorb moisture, and, upon dry-\\ning, are liable to warp and twist. They furthermore be-\\ncome brittle when heated.\\nSheets of insulation made up from pieces of scrap mica\\ncemented together by linseed oil or preparations of shellac,\\nwhen carefully constructed with lapped joints, exhibit\\nnearly as good insulating and dielectric properties as sheet\\nmica. While not perfect mechanically, these sheets permit\\nof bending better than pure mica.\\nVulcabeston, which is a preparation of asbestos and rub-\\nber, exhibits fairly good insulating and mechanical quali-\\nties, and is especially fitted for higher temperatures. Its\\ndielectric strength is about T of that of mica.\\n6. Divided Circuits. If a current be flowing through", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0019.jp2"}, "20": {"fulltext": "8\\nDYNAMO ELECTRIC MACHINERY.\\nR, the undivided part of the circuit shown in Fig. I, and\\nif I x and I 2 be the currents flowing in the shunt resistances\\nR x and R 2f then I t f 2 and, since the pressure E\\nupon each shunt is the same, by Ohm s law,\\nE a r E\\n1 R 2== R\\nThe currents in the branches of a divided circuit are in-\\nversely as the resistances of the branches.\\nIf R e be a /single resistance, that substituted for the\\nshunted resistances R t and R 2 will leave unchanged, then,\\nby Ohm s law,\\nR e R x R 2\\nor R,\\nR\\\\ R 2\\nR x R,\\n1 1\\nR x R 2\\nThe resistance equivalent to a number of shunted resistances\\nis equal to the reciprocal of the sum of the reciprocals of the\\nseparate resistances.\\nRl\\nt\\nnnnnnnnnnnnrw^nr\\n1\\nFig. 1.\\n7. Power of Electric Current. A difference of poten-\\ntial e between two points requires e ergs of work to bring", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0020.jp2"}, "21": {"fulltext": "ELECTRICAL LAWS AND FACTS. 9\\na unit quantity of electricity from one point to the other.\\nA unit of quantity is one absolute unit of current flowing\\nfor one second. Hence a current i flowing for t seconds with\\na difference of potential e does eit ergs of work. Likewise\\na current flowing seconds gives coulombs of quantity,\\nEit\\nand with a difference of potential of E volts does ergs\\nof work. Hence the work per second or the power is 7\\nabsolute units. The practical unit of power is the watt,\\nand equals io 7 absolute units. Hence, remembering that\\nby Ohm s law E IR the power of a current in\\nWatts \u00c2\u00a31= PR.\\nFor commercial currents and voltages the watt is a need-\\nlessly small expression, hence the kilowatt 1,000 watts)\\nis generally used as the unit of electrical power. It is repre-\\nsented by the abbreviation k. w. The horse-power is\\nequal to 746 watts, or approximately three-fourths of a k.w.\\n8. Heat Developed by a Current, When a current\\ndoes work in overcoming a resistance R, the work per-\\nformed is converted into heat. By the last article the\\nwork thus done per second, or the power expended, will be\\nPR watts. Since this rate of production of heat is often\\nof no service, this expenditure of power is generally called\\nthe PR loss.\\nThis production of heat causes a rise of temperature in\\nthe conductor, and the temperature will continue to rise till\\nthe heat generated per second by the PR loss is exactly\\ncounterbalanced by the rate of dissipation of heat by con-\\nduction, convection, and radiation.\\nThe necessary resistances of electrical machines involve", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0021.jp2"}, "22": {"fulltext": "IO DYNAMO ELECTRIC MACHINERY.\\nthe production of heat in their operation (as does also fric-\\ntion and reversal of magnetism), which causes a rise of tem-\\nperature. As insulating materials can survive only moder-\\nately high temperatures, such machines must be designed\\nto operate without becoming too hot. This is accomplished\\nby decreasing the PR loss, by increasing the radiating sur-\\nface, and by supplying ventilation.\\n9. Fuses. These are devices intended to protect cir-\\ncuits from destruction or damage due to an excessive flow\\nof current through them. They protect them by being\\nthemselves destroyed. They are generally made of lead\\nor alloys of lead. Lead is liable to become oxidized after\\nhaving been installed for some time. It is then liable to\\nform a tube of hard oxide, which is sufficiently strong to\\nhold molten lead in its interior, so as to maintain an elec-\\ntrical contact in the circuit which should be broken. Some\\nalloys are not open to this objection. These alloys, in\\nthe form of wires, strips, or ribbons, are fastened at each\\nend to copper terminals which are slotted to fit into fuse\\nreceptacles. The wire with its terminals is called a fuse\\nlink. Such a link is shown in Fig. 2.\\nFig. 2.\\nCopper wires are sometimes used as fuses on trolley cars,\\nbut the high melting point of copper prohibits its use as a\\nprotective device on house circuits.\\nThe current which will fuse a wire of lead alloy depends\\nin magnitude upon the length of the wire. Short lengths", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0022.jp2"}, "23": {"fulltext": "ELECTRICAL LAWS AND FACTS. II\\nof a wire of given cross-section and given material will\\ncarry stronger currents than longer lengths. The heat\\nwhich is generated in the short ones escapes more rapidly,\\nowing to the larger masses of metal commonly forming the\\nterminals of the fuse. Fuses are rated to carry a given\\namperage, and the rating is stamped upon the copper termi-\\nnals. According to the national code the fuses must, how-\\never, be able to carry indefinitely without melting such a\\nnumber of amperes that the rated capacity is but 80 per\\ncent of it. This permits the fuse to carry without melting\\n25 per cent above the rated capacity.\\nFig. 3.\\nFor high voltages, and for large amperages, inclosed\\nfuses are sometimes used, in which the fusible conductor is\\nsurrounded by a packing of finely divided powder in which\\nborax is included as an element most desirable. Such a\\nfuse is shown in Fig. 3.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0023.jp2"}, "24": {"fulltext": "12 DYNAMO ELECTRIC MACHINERY.\\nCHAPTER II.\\nMAGNETIC LAWS AND FACTS.\\nio. Strength of Magnet Pole A unit magnet pole is\\none which will repel an equal like pole, when at a distance\\nof one centimeter, with a force of one dyne.\\nIt follows from this definition that a pole m units strong\\nwill repel a like unit pole with a force of m dynes. The\\nforce exerted between two magnetic poles varies inversely\\nas the square of the distance between them. Hence the\\nforce exerted between two magnetic poles of strengths m\\nand w! when ^centimeters apart is defined by the equation\\nd 2\\nii. Intensity of Magnetic Field. A magnetic field is\\nof unit strength or intensity when a unit magnet pole placed\\ntherein is acted upon by a force of one dyne, or when a\\nmagnet pole m units strong is acted upon by a force of\\nm dynes. The strength of a field is usually represented\\nby 3C.\\n12. Magnetic Field and Lines of Force. The space\\naround a magnet where its action is felt is termed the field\\nof that magnet. This field may conveniently be consid-\\nered as permeated by lines of force. These lines represent\\nthe direction of the force exerted by the magnet, and by\\ntheir closeness to each other show the magnitude of this\\nforce.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0024.jp2"}, "25": {"fulltext": "MAGNETIC LAWS AND FACTS. 13\\nThe student must not get the impression that, because\\nthe lines spread apart, a point in the field could be chosen\\nwhere there would be no line. These lines may well be\\nconsidered as tubes or pencils of force, filling all the space\\naround the magnet.\\nThe lines of force contained in any plane passed through\\nthe magnet pole compose a magnetic spectrum, which can\\nbe made visible by the familiar experiment of sprinkling\\niron filings on a paper, which is laid over a magnet, and by\\ngently tapping it.\\nBy convention one line of force per square centimeter is\\nconsidered to represent a field of unit strength, the square\\ncentimeter being so taken that it is at all points perpendic-\\nular to the lines cutting it. Hence the strength or inten-\\nsity 3C of any field can be expressed by the number of\\nlines of force per square centimeter.\\nSuppose a sphere of one centimeter radius to be circum-\\nscribed about a unit magnet pole. Another unit pole at\\nany point on the surface of this sphere will be acted upon\\nby a force of one dyne. Hence there exists a unit field at\\nany point on this surface. But there are 4 ?r square centi-\\nmeters on this surface, and each square centimeter will\\nbe cut by one line of force. Therefore, there emanate\\nfrom a unit magnet pole 4 it lines of force. Similarly a\\nmagnet pole of strength m sends out 4 it m lines of force.\\nA magnetic field is said to be uniform when it has the\\nsame JC at every point therein, or when the lines of force\\nare parallel.\\n13. Electro-Magnetic Induction. In 1831 Faraday and\\nHenry independently discovered that when a conductor was\\nmoved in a magnetic field, an electromotive force was set", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0025.jp2"}, "26": {"fulltext": "14\\nDYNAMO ELECTRIC MACHINERY.\\nup in the conductor. This phenomenon is the foundation\\nof all modern electrical engineering.\\nAn absolute unit of E.M.F. is produced when a conduc-\\ntor cuts one line of force per second. If the conductor\\ncuts two lines in the second, or one line in half a second,\\nthen two units are produced.\\nIf, in the short interval of time, dt seconds, d j lines be\\ncut, then during that interval the value of the induced\\nE.M.F. will be\\nd f\\nor,\\ni d j\\nE\\n10 dt\\nvolts.\\nThe negative sign is used because the induced E.M.F.\\ntends to send a current in such a direction as to demag-\\nnetize the field. When of no con-\\nsequence the negative sign will\\nhereafter be omitted.\\nIf a conductor, Fig. 4, centi-\\nmeters long moves parallel to itself\\nwith a uniform velocity of v cen-\\ntimeters per second across a uni-\\nform magnetic field of strength\\n3C, its path making an angle a with\\nthe direction of the lines of force,\\nthen the number of lines cut per\\nsecond is Wlv sin a, and since the\\nrate of cutting is uniform, the E.M.F. at any instant is\\ne 3Zlv sin a.\\nIf there be a non-uniformity in the rate of cutting lines,\\ndue either to an uneven field or an irregular motion, then\\nT\\nFig. 4-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0026.jp2"}, "27": {"fulltext": "MAGNETIC LAWS AND FACTS. 1 5\\nthe average value of the induced E.M.F. associated with\\nthe cutting of lines in the time, t seconds, will be e av\\nFor suppose the time to be divided into equal and small\\nperiods havirg a duration of At seconds. Furthermore,\\nsuppose that during these successive periods A A A\\netc., lines be cut respectively. Then the induced E.M.F. s\\nduring these periods, which may be represented by e e\\netc., respectively, will be as follows\\nd\\nA\\nA/\\ne\\nA*\\nAt\\ne\\nA f ,n\\nA/\\nAdding these equations, and then dividing by gives the\\nequation above, viz.,\\n*av j or E av volts.\\nThe average value of the induced E.M.F. is therefore inde-\\npendent of the magnitude of the instantaneous values.\\nIf a loop of wire revolve, uniformly or otherwise, in a\\nmagnetic field which is uniform or otherwise, its sides cut\\nlines of force at various rates. The instantaneous E.M.F.\\nin the whole loop will be as before.\\nd$\\ne r\\ndt\\nwhere is the number of lines that links with, or that\\npasses through, the loop. If the loop be of n turns, then", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0027.jp2"}, "28": {"fulltext": "i6\\nDYNAMO ELECTRIC MACHINERY.\\nthe pressure will be n times as great, or during the inter-\\nval dt,\\nnd j\\nE\\n\u00e2\u0096\u00a0fdt\\n14. Direction of Induced E.M.F. The direction of\\nflow of a current induced in a closed circuit by mov-\\ning it in a magnetic field is best represented by drawing\\nthe conventional representation of the three dimensions\\nof space. If the flux be directed upwards, and the motion\\nof the conductor be to the right, then the E.M.F. will tend\\nto send a current toward the reader. If any one of these\\nconditions be changed it necessitates the change of one of\\nthe others, and conversely the change of any two leaves\\nFig. 5*\\nMotion\\nFig. 6.\\nthe third unaltered. About the same idea is represented\\nin Fleming s Rule, which is as follows\\nLet the index finger of the right hand point in the di-\\nrection of the flux, and the thumb in the direction of the", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0028.jp2"}, "29": {"fulltext": "MAGNETIC LAWS AND FACTS. 17\\nmotion. Bend the second finger at right angles with the\\nthumb and index finger, and it will point in the direction\\nof the EM.F.\\nAnother rule is\\nStand facing a north magnetic pole. Pass a conductor\\ndownward. The current tends to flow to the left.\\n15. Inductance. Nearly every electrical circuit which\\nhas a current flowing in it has lines of force linked with it,\\ndue to that current. When the circuit is opened the dis-\\nappearance of the lines is accompanied by a cutting of the\\ncircuit by those lines, and the cutting results in the pro-\\nduction of an E.M.F. This is called the E.M.F. of self-\\ninduction. Its magnitude is dependent upon the rapidity\\nwith which the field disappears, and upon a constant deter-\\nmined by the geometric shape of the circuit and the char-\\nacter of the medium in which it is placed. This constant\\nis called the self-inductance or the coefficient of self-induc-\\ntion of the circuit. It is generally represented by the\\nletter L, and is that coefficient by which the time rate of\\nchange of current in the circuit must be multiplied in order\\nto give the E.M.F. induced in the circuit. Its absolute\\nvalue is numerically represented by the number of lines of\\nforce linked with the circuit per absolute unit of current in\\nthat circuit. Its practical unit is io 9 times as large as the\\nabsolute unit, and is called the henry. In a given circuit it\\nvaries as the square of the number of turns of wire. Two\\ncircuits may exercise a mutually inductive action upon each\\nother, and an E.M.F. may be induced in one by a change\\nof current in the other. This is called the E.M.F. of\\nmutual induction. In magnitude it depends upon the shape\\nand position of the two circuits, and upon the character", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0029.jp2"}, "30": {"fulltext": "18 DYNAMO ELECTRIC MACHINERY.\\nof medium in which they are placed. It is also dependent\\nupon a constant which is called the mutual inductance or\\ncoefficient of mutual induction of the two circuits. It is\\ngenerally represented by the letter M. It is that coeffi-\\ncient by which the time rate of change of the current in one\\nof the circuits is multiplied in order to give the E.M.F.\\ninduced in the other circuit. Its absolute value is numeri-\\ncally equal to the number of lines of force linked with one\\nof the circuits per absolute unit of current in the other cir-\\ncuit. Its practical unit is the same as the practical unit\\nof self -inductance, that is the henry, and is io 9 times as\\nlarge as the absolute unit. The coefficient of mutual in-\\nduction varies directly as the number of turns of wire in\\neither circuit.\\n16. Quantity of Electricity Traversing a Circuit Due\\nto a Change of Flux Linked with it. In many dynamo\\ntests, and in many magnetic investigations, it is necessary\\nto measure, generally by means of a ballistic galvanometer,\\nthe quantity of electricity traversing a circuit due to a\\nchange of flux linked with it. If the circuit have a resist-\\nance of r and in dt time the flux linked with n turns\\nchanges by dfa then the instantaneous current\\nnd f\\n._~dt\\nr\\nBut the quantity, q idt, hence\\nndd\\nwhich is independent of time. So if the flux change from\\nt t to f then", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0030.jp2"}, "31": {"fulltext": "MAGNETIC LAWS AND FACTS. 19\\nor Q microcoulombs.\\n100 ./c\\n17. Work Performed by a Conductor Carrying a Current\\nand Moving in a Magnetic Field. Let a conductor carry-\\ning a constant current i be moved in a direction perpen-\\ndicular to itself and to the lines of force of a magnetic field.\\nSuppose it to move for dt seconds, and in that time to cut\\nd f lines of force. Then the induced E.M.F. e will be\\n-f. The quantity of electricity dq that has to traverse\\ndt\\nthe circuit against this E.M.F. during the time dt will\\nbe idt. Since potential is a measure of work, the work\\nrequired to carry dq units of electricity against a difference\\nof potential e is edq ergs. Hence the work in ergs,\\nd b\\ndw edq idt X \u00e2\u0080\u0094j- idcf\\nTherefore the current i, in cutting lines of force, per-\\nforms the work\\nw i$ ergs.\\nFrom this it is seen that the work done by a conductor\\ncarrying a current and cutting lines of force is independent\\nof the time it takes to cut them.\\nIn the above discussion, if the field be not uniform or\\nthe motiqn be not uniform, the value of e will not be the\\nsame for each instant of time. But since the result\\nobtained is independent of time, it is immaterial how the\\nlines are arranged, and how the rate of cutting varies.\\n18. Magnetic Potential. The magnetic potential at\\nany point is measured by the work required to bring a unit\\nmagnet pole up to that point from an infinite distance.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0031.jp2"}, "32": {"fulltext": "20 DYNAMO ELECTRIC MACHINERY.\\nThe difference of magnetic potential between any two\\npoints is measured by the work in ergs required to carry a\\nunit magnet pole from one to the other. The difference\\nof magnetic potential is a measure of the ability to send\\nout lines of force, or to set up a magnetic field.\\n19. Magnetomotive Force of a Circular Circuit Carry-\\ning a Current. A thin circular conductor carrying a cur-\\nrent forms a magnetic shell. If a unit magnet pole be\\ntaken from the top side of a shell, and carried around to\\nthe bottom side, work must be\\ndone, and this work is a measure\\nof the difference of potential be-\\ntween the two sides of the shell.\\nIt is immaterial whether the\\n^K^. pole be carried from one side of\\n%^-j^ the shell to the other, or the\\nFig. 7.\\nshell be turned bottom side up\\naround the pole. In the latter case it is clear that all the\\nlines emanating from the pole will be cut once, and once\\nonly, by the conductor, wherefore 4?r lines will have been\\ncut.\\nIf current i flows in the conductor, then, by 17,\\nWork in ergs i f 4 tt/.\\nIf there be n turns of the conductor, each line of force\\nwill be cut times, and the work will be ^irni ergs.\\nHence the difference of potential between the two sides\\nof a thin magnetic shell is 4 irni or l^ 7\\n4tt IO\\nIn this expression is a constant, and it is convenient\\nto regard ;*/as a single variable. In connection with it the", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0032.jp2"}, "33": {"fulltext": "MAGNETIC LAWS AND FACTS. 21\\nterm ampere-turns is employed, and this is frequently\\nwritten nL\\nHere the same argument holds as in 1 7, that the inten-\\nsity of field and the rate of cutting lines will vary as the\\npole is in different parts of the path. But the total num-\\nber of lines cut is the same in any case, so the expression\\nfor work and potential is true, no matter what path the pole\\ntakes.\\n20. Force Exerted on a Field by a Conductor Carrying a\\nCurrent When a conductor moves in a field perpendicu-\\nlar to itself and to the lines of force, then, from \u00c2\u00a717,\\nWork i f ergs.\\nIf the conductor be centimeters long, and traverses a dis-\\ntance of s centimeters through a uniform field of strength\\nJC (JC lines per sq. cm.), then\\nf AJC,\\nand the\\nWork Us JC ergs.\\nBut\\nWork force X distance Fs /Zr JC.\\nr/ f xp\\nF JC dynes.\\n10\\n21. The Solenoid. A uniformly wound, long, straight\\ncoil, carrying a current i, produces a uniform field JC at its\\ncenter. This coil is called a solenoid, and may be consid-\\nered as composed of magnetic shells arranged at equal dis-\\ntances from each other. It takes 4-iri ergs to move a unit\\nmagnet pole from one side of a shell to the other 19),\\nand 47rm ergs to pass it through the n consecutive shells", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0033.jp2"}, "34": {"fulltext": "22 DYNAMO ELECTRIC MACHINERY.\\nof the solenoid. If these n shells occupy a length on the\\nsolenoid of centimeters, then\\nWork force X distance 30,/= 4izin ergs,\\nand the magnetizing force, that is, the strength or intensity\\nof field, in the solenoid is\\n\\\\TTllI\\nX\\n10\\n22. Permeability. The same difference of magnetic\\npotential between two points will produce more lines of\\nforce in iron than in air. Iron is then said to be more per-\\nmeable than air, or to have a greater permeability. If a\\ndifference of magnetic potential could set up, at a certain\\nplace, a field of strength X, with air as a medium, and one\\nof strength (fc, with some other substance as a medium,\\nthen the ratio expresses the permeability of that sub-\\nstance. This ratio is usually represented by /x. As 3C\\nvaries directly with the magnetic difference of potential, it\\nbecomes a measure of it. Therefore 3\u00e2\u0082\u00ac is called the mag-\\nnetizing force and B the flux density y the magnetic density,\\nor the induction per square centimeter. For air, vacuum,\\nand most substances fi I. For iron, nickel, and cobalt\\nhas a higher value, reaching, in the case of iron, as high\\nas 3000. Bismuth, phosphorus, water, and a few other sub-\\nstances, have a permeability very slightly less than unity.\\nA substance for which /x o would insulate magnetism.\\nThere is no such substance.\\nThe total magnetic flux, j which passes through an\\narea of A square centimeters, in which the magnetic density\\nis is represented by the equation\\nA (B.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0034.jp2"}, "35": {"fulltext": "MAGNETIC LAWS AND FACTS.\\n23\\nThe permeability of air is constant for all magnetizing\\nforces. This is not the case with iron and other substances\\nwhich have a permeability greater than unity. The value\\nof /a, and 3C, which are connected by the relation (B //,3C,\\nare given in the following table for average commercial\\nwrought iron, for cast iron, and for steel. The relations\\nwhich exist between and 3C are also shown in Figs. 8, 9,\\nand 10. These curves are technically known as (B-3C\\ncurves.\\nDATA FOR (B-OC CURVES.\\nAVERAGE FIRST QUALITY METAL.\\nWrought and\\nCast I\\nRON.\\nCast Steel.\\nAmpere-\\nAmpere-\\nSheet\\nRON.\\n5C\\nturns\\nper Cen-\\nturns\\nper Inch\\nKilo-\\nKilo-\\nKilo-\\ntimeter\\nLength.\\nLength.\\nlines\\nper\\nSq. In.\\nlines\\nper\\nSq. In.\\n(E\\nlines\\nper\\nSq. In.\\n10\\n7-95\\n20.2\\n1 1 800\\n74\\n3900\\n25.2\\n12000\\n77\\n20\\n15.90\\n40.4\\n14000\\n90\\n5500\\n35-5\\n13800\\n89\\n30\\n23-85\\n60.6\\n15200\\n98\\n6500\\n42.0\\n14600\\n94\\n40\\n31.80\\n80.8\\n15800\\n102\\n7IOO\\n457\\n15400\\n99\\n5\u00c2\u00b0\\n3975\\nIOI.O\\n16400\\n106\\n7700\\n49-5\\n16000\\n!03\\n60\\n4770\\n121. 2\\n16800\\n108\\n8200\\n53-o\\n16400\\n106\\n80\\n63.65\\nl6l.6\\n17200\\nIII\\n8900\\n57.2\\n16700\\n108\\n100\\n79.50\\n202.0\\n17600\\n114\\n9300\\n60.0\\n17600\\nIJ 3\\n125\\n99.70\\n252.5\\n17800\\n115\\n9700\\n62.4\\n18200\\n117\\n150\\n119.25\\n3\u00c2\u00b03\\n18000\\n116\\nIOIOO\\n65.8\\n18600\\n120\\n5C= 1.258 (nl per cm.) .495 (/z/per in.). (B I 55 (0 per sq. in.).\\n23. Things Which Influence the Shape of the (B-JC Curve.\\nIn general all substances mixed with or alloyed with iron\\nlower its permeability. In steel and cast iron the per-\\nmeability seems to be in inverse proportion to the amount\\nof carbon present. Carbon in the graphitic (not combined)\\nform lowers the permeability less than carbon when com-\\nbined. In cast iron and cast steel such substances as tend\\nto give softness and greater homogeneity to the metal", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0035.jp2"}, "36": {"fulltext": "24\\nDYNAMO ELECTRIC MACHINERY.\\nIll per centimeter 16\\nTOLL per inch\\nWROUGHT AND SHEET IRON\\n129\\n20000\\n18000\\n16000\\n14000\\n12000\\n10000\\n8000\\n6000\\n4000\\n2000\\n103\\n90\\nsX\\nfit*\\nd\\ntag\\nj\\nt 71\\n1\\nI\\n^7\\n^y\\n1\\nt. 65\\nJ\\no\\n.3 52\\n39\\n26\\n13\\ni\\n1\\nJ\\n4\\n5\\nc\\n7\\n3\\nJ\\na\\n100\\n110\\n120\\nr\\n\u00e2\u0096\u00a030\\nPermeability\\nFig. 8.\\nCAST IRON\\nfc 19.5\\n13\\n6.5\\n10000\\n0000\\n(B\\n5000\\n\u00e2\u0080\u0094i\\nh\\n4000\\n1\\n1\\nRdon\\n000\\nJ\\nr\\nt\\ny\\n1\\nu\\n10 20 30 40 50 60 70\\n)0 1\\n1\\nw\\n7t I per centimeter 16\\nn I per inch\\nPermeability// _ 100\\nFig. 9", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0036.jp2"}, "37": {"fulltext": "MAGNETIC LAWS AND FACTS.\\n25\\nCAST STEEL\\n18000\\n103\\n14000\\n(B\\n12000\\nA 90\\n\u00e2\u0080\u00a2S\\n5 a\\ng^\\nZ 05\\nS ^T7T7^\\n_^\\n8000\\n6000\\n4000\\n.a 52\\nR\u00c2\u00a3\\nSID\\nUA\\nL-MAG\\nNE\\nTIS\\nW i n\\n69\\n13\\nnl per c\\ni) I\\n10 20 3\\nI\\n5 -1\\n43 50 55 60 65 70 7\\nntimeter 8 16 24 32 40 48 56\\n91/ per iuch 2.0. 40 60 80 100 120 140\\nPerineability jM 1000 2000\\nAC\\nFig. io.\\nwhen present in limited amounts, say 2 per cent, increase\\nthe value of /a. Aluminum and silicon act in this way.\\nThe physical condition of the metal also affects its per-\\nmeability. Chilling in the mold, when casting, lowers it, as\\ndoes tempering, or hardening the metal by working it. On\\nthe other hand, annealing increases the permeability.\\nA piece of iron or steel, subjected to a small magnetizing\\nforce, has its permeability increased by increasing the tem-\\nperature until a critical temperature is reached, when it falls\\noff rapidly to almost unity. For stronger magnetization\\nthe permeability does not rise so high at the critical tem-\\nperature, and does not fall off so sharply after it. The\\nvalue of this critical temperature lies between 650 C. and\\n900 C, depending on the test piece.\\n24. Reluctance and Permeance. In the flow of mag-\\nnetic lines of force the reciprocal of the permeability is", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0037.jp2"}, "38": {"fulltext": "26 DYNAMO ELECTRIC MACHINERY.\\ncalled the reluctivity. The total reluctance, tending to\\noppose the passage of magnetic lines under the influence\\nof a magnetic difference of potential, is directly as the\\nlength and the reluctivity of the medium and inversely as\\nits cross-section. Hence the total magnetic resistance or\\n_ length\\nReluctance reluctivity.\\ncross-section\\nReluctivity is usually represented by Hence for\\na medium of cross-section A square centimeters and length\\ncentimeters, the reluctance\\n1 a p.\\nPermeance is the reciprocal of the reluctance, hence the\\npermeance\\n(P P 7 t\\nIt must be remembered that p and /x are not constant for\\nany one substance, but depend for their values upon the\\nstrength of the magnetizing force JC which is acting upon\\nthe substance.\\n25. Relation Between Magnetomotive Force, Magnetic\\nFlux, and Reluctance. These quantities are related to\\neach other the same as are E.M.F., current, and resistance,\\nviz\\n__ Magnetomotive Force\\nReluctance\\nIn this respect electric current and magnetic lines are\\nsimilar. However, while electric circuits, in the main, ex-\\nist in media of zero electric conductivity, and therefore\\npermit of accurate calculations, there being no appreciable\\nleakage, magnetic circuits must be situated in media which", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0038.jp2"}, "39": {"fulltext": "MAGNETIC LAWS AND FACTS.\\n27\\nhave permeabilities of at least unity. In the latter case\\nmuch leakage is present, and precise calculations are out of\\nthe question. In the designing of dynamo electric ma-\\nchinery, however, one or more paths of low reluctance are\\npresented to the magnetizing force, and these are pro-\\ntected by being so shaped that leakage paths offer a com-\\nparatively high reluctance.\\n26. Hysteresis. If a piece of iron become magnetized,\\nand the magnetizing force be then removed, the iron does\\nFig. 11.\\nnot become completely demagnetized. A certain magnet-\\nizing force in the opposite direction must be used to bring\\nit to a neutral state. This phenomenon has been termed\\nhysteresis. Because of hysteresis a (B-3C curve taken with\\ncontinuously increasing values of 3C to the maximum and", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0039.jp2"}, "40": {"fulltext": "28 DYNAMO ELECTRIC MACHINERY.\\nthen with continuously decreasing values of 3C to a negative\\nmaximum, and so on, will assume the shape shown in Fig.\\nn. The distance O A represents the coercivity, that is,\\nthe magnetizing force necessary to bring the iron from a\\nmagnetic to a neutral state. The distance O C represents\\nthe retentivity, that is, the amount of magnetic induction\\nleft in the iron after the magetizing force has been removed.\\nThe area inclosed by the curve represents the energy lost\\nin carrying the iron through one cycle, i.e., from a maximum\\nmagnetization to a maximum in the opposite direction and\\nback to the orginal condition.\\nFor suppose the magnetization to be due to a current\\nflowing in a solenoid of n turns. If, in a short interval of\\ntime dt a change of d f be made in the flux which is linked\\nwith the solenoid, then this change will induce an E.M.F.\\nin the solenoid which during the interval of time dt will be\\nequal to\\nZ7 _ nd\\nioV/\\nvolts.\\nDuring this time work must be performed to maintain this\\ncurrent and its magnitude is\\nEIdt= n J?t,\\nfor Idt represents the quantity of electricity which is trans-\\nferred from one point to another, between which there ex-\\nists a difference of potential E. Now cf A($ 22) and\\nhence d$ Ad Furthermore, nl IOJC/ 21). Hence\\nthe work during the time dt is 4 w\\nAl\\nEldt _ je /(B joules.\\nI0 7 47T", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0040.jp2"}, "41": {"fulltext": "MAGNETIC LAWS AND FACTS. 29\\nSupposing the magnetizing force to vary cyclically, taking\\nT seconds to make one cycle, then the work per cycle is\\nmax\\nai r\\n\u00c2\u00a3IT= 7 I 3C//(fc joules.\\nio 7 4ttJ\\nmax\\nIf the number of cycles completed in one second bey, then\\nf and the\\nin watts, equals\\nf and the work in joules per second, that is, the power\\nEI= J JC^CB =-^-V /volume 3C\\nIO 47Tj _^ IO 8 J _ r,\\nmax ^^max\\nThe integral expression is evidently the area contained by\\nthe hysteresis loop.\\n27. Steinmetz s Law The value of the integral ex-\\npression is dependent upon max upon the retentivity of\\nthe kind of iron, and upon its coercivity. Steinmetz has\\nshown that for all practical purposes the value of the inte-\\ngral may be expressed by the empirical formula\\ns-\\nl~ U\u00c2\u00aemax\\n3Zd( v (B\u00c2\u00a3 BO\\nmax\\nwhere rj is a constant depending upon the kind of iron.\\nIts value is given in the following table\\nHYSTERETIC CONSTANTS.\\nBest soft iron or steel sheets 0.00 1\\nGood soft iron sheets 0.002\\nOrdinary soft iron 0.003\\nSoft annealed cast steel 0.008\\nCast steel 0.012\\nCast iron 0.016\\nHard cast steel 0.025", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0041.jp2"}, "42": {"fulltext": "30 DYNAMO ELECTRIC MACHINERY.\\nThe hysteretic constant, if at first small, grows with age.\\nIts increase can be hastened by continued heating. The\\nincrease may amount to 200 per cent. Annealing, while it\\nincreases the permeability, also increases the hysteretic\\nconstant, if it be originally very small.\\nThe magnitude of the hysteretic constant is largely de-\\npendent upon the mechanical structure of the iron. To\\nattain the smallest value the iron should not be of homoge-\\nneous structure, but should have a greater density in the\\ndirection perpendicular to the direction of flux.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0042.jp2"}, "43": {"fulltext": "ARMATURES. 31\\nCHAPTER III.\\nARMATURES.\\n28. Dynamos Dynamos may be defined as machines\\nto convert mechanical energy into electrical energy by\\nmeans of the principle of electromagnetic induction. In\\nall commercial machines the mechanical energy is supplied\\nin the form of rotation, and the electrical energy is deliv-\\nered either as direct current or alternating current.\\nThese machines are also frequently called generators.\\n29. Principle of the Action of a Dynamo. If a loop of\\nwire be revolved in a magnetic field about ah axis perpen-\\ndicular to the lines of force, as in Fig. 12, then each side\\n(but not the ends) of the loop is a conductor moving across\\nthe lines of a magnetic field, and as such will have an\\nE.M.F. induced in it. Since the motion of one conductor\\nis up while that of the other is down, the directions of the\\ninduced E.M.R s in the two sides will be opposite to each\\nother, and since they are on opposite sides of a loop, the\\npressure will be cumulative i. e., instead of neutralizing\\neach other, the two pressures will be added to each other.\\nIf now the two ends of the wire from which the loop is\\nmade be respectively connected with slip rings, and a cir-\\ncuit be completed through contacts sliding on them, a cur-\\nrent will flow. When the loop, in its revolution, reaches a\\nposition (as illustrated in Fig. 1 2) such that the conductor", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0043.jp2"}, "44": {"fulltext": "32\\nDYNAMO ELECTRIC MACHINERY.\\nthat was previously moving upward begins to move down-\\nward, then the direction of the induced E.M.F. will be\\nchanged in both sides of the loop, and the direction of the\\nFig. 12.\\ncurrent through the circuit will be changed. For each\\ncomplete revolution the current changes direction twice.\\nIt is an alternating current, and the supposed machine is\\nan alternating current dynamo, or simply an alternator.\\n30. The Principle of the\\nCommutator A commu-\\ntator is used on the shaft of\\na machine when it is de-\\nsired to get a direct or rec-\\ntified current. For the\\nsingle loop in the above\\ncase, the commutator (Fig.\\n13) would consist of two similar cylindrical parts of metal,\\ninsulated from each other, and affording sliding contact for\\nFig. 13.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0044.jp2"}, "45": {"fulltext": "ARMATURES.\\n33\\ntwo brushes. One end of the wire of the loop is attached\\nto one piece of the commutator, and the other to the other.\\nThe brushes are so placed that at the instant the in-\\nduced E.M.F. in the loop changes its direction, the brushes\\nslide across from one segment of the commutator to the\\nother, and thus the current, while reversed in the loop, is\\nFig. 14.\\nleft flowing in the same direction in the outside circuit.\\nIf the loop were wound double before the ends were at-\\ntached to the commutator segments, and if the speed of\\nrevolution and the strength of the magnetic field were both\\nmaintained constant, twice the E.M.F. would be produced,\\nbut no more commutator segments would be necessary\\n(Fig. 14).\\nIn the above cases at the instants of commutation there\\nwould be no E.M.F produced, and hence the current would\\nfall to zero twice every revolution. If two coils were placed\\n90 apart, one or the other would always be cutting lines\\nof force. Hence at no time could the pressure be zero.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0045.jp2"}, "46": {"fulltext": "34\\nDYNAMO ELECTRIC MACHINERY.\\nTo satisfactorily collect current from this arrangement re-\\nquires four commutator segments and a system of connec-\\ntions similar to that shown\\nin Fig. 15. In this case\\nthe E.M.F. would fluctu-\\nate, but not so badly as in\\nthe previous case. If we\\nincrease the number of\\nloops, and correspondingly\\nincrease the number of\\ncommutator segments, we\\ndecrease the fluctuation\\nof the E.M.F. until it be-\\ncomes practically constant. In a bipolar machine with 12\\ncommutator segments the fluctuation is 1.7 per cent of the\\ntotal E.M.F.\\nFig. 15.\\n31. The Armature In a dynamo, the loops of wire in\\nwhich E.M.F. is induced by movement in a magnetic field,\\ntogether with the iron core that sustains them, with the\\nnecessary insulation, and with the parts connected imme-\\ndiately thereto, constitute the armature of a dynamo. The\\nconductors in which the\\nE.M.F is generated are\\ncalled the inductors. An\\narmature in which both\\nsides of the loop of wire\\ncut lines of force, as in\\nthe cases just described,\\nis called a Drum Arma-\\nture. A kind of armature less generally used is the Ring\\nArmature y illustrated diagrammatically in Fig. 16. Here\\nFig. 16.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0046.jp2"}, "47": {"fulltext": "ARMATURES.\\n35\\nthe lines of force emanating from the N. pole of the field\\nmagnets flow through the iron core of the ring, and very-\\nfew across the air space inside the ring. Hence when\\nwires are wound on the ring, and the whole is revolved\\nabout an axis perpendicular to the plane of the ring, only\\nthe wires on the outside face of the ring cut lines of force,\\nthose on the inside serving only to complete the electrical\\ncircuit. So a smaller portion of the wire on a ring arma-\\nture is in action than on a drum armature.\\nA drum armature of large diameter and of short length\\nin the axial direction has more wire exposed on its ends\\nthan on its periphery. The pole pieces are sometimes\\nplaced at the ends, and the armature is then called a Disk\\nArmature. This type is seldom used in this country.\\n32. The Field Magnets. Almost all dynamos have\\ntheir magnetic fields produced by electro-magnets. These\\nFig. 17.\\nare called the field magnets. In small machines these are\\nusually bipolar, i.e., having one N. and one S. pole, with", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0047.jp2"}, "48": {"fulltext": "36 DYNAMO ELECTRIC MACHINERY.\\nthe armature revolving between. In large machines it is\\nusual to use multipolar field magnets, in which any even\\nnumber of poles alternately N. and S. are arranged in a\\ncircle with their faces concentric with the armature.\\nBipolar machines are made in many forms, a few of\\nwhich are shown in Fig. 17.\\nThe magnetizing coils may be on both legs of the mag-\\nnet, on one leg, or on the yoke which connects the two legs.\\nIn the double horse-shoe type there are four windings, one\\non each of the four legs. Such a field is sometimes said\\nto be of the consequent pole type.\\n33. Capacity of a Dynamo. By 13, in a bipolar\\nmachine the average pressure between brushes equals the\\nproduct of the number of lines cut into the number of in-\\nductors cutting them, divided by the time in seconds of\\none revolution. Since each line is cut twice in one revolu-\\ntion by each conductor, the formula for the E.M.F. pro-\\nduced by the machine is\\nV*S\\n60 IO 8\\nwhere V is the number of revolutions per minute, j the\\ntotal flux through the loops, and 5 the number of inductors.\\nIn drum armatures S twice the number of loops in ring\\narmatures 5 the number of loops.\\nThe capacity of a machine is measured by the watts it\\ncan send out, hence the capacity varies as EL It is seen\\nfrom the foregoing formula that the E of any machine may\\nbe increased by increasing either V, or .S.\\nThe value of Fis limited, (1) by considerations of me-\\nchanical safety and economy, and (2) by the desirability, in\\nthe case of a dynamo, of directly connecting it to the steam", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0048.jp2"}, "49": {"fulltext": "ARMATURES. 37\\nengine or other prime mover, and in the case of a motor\\nthe connection of it to the machine it operates. The speed\\nof small machines is greater than that of larger ones but\\nthe peripheral velocity, that is, the velocity of a point on\\nthe exterior of the armature, for all sizes, lies between 25\\nand 100 feet per second on belt-driven machines, and be-\\ntween 25 and 50 feet per second on direct connected\\nmachines. On large (say 2,000 k.w.) multipolar machines,\\nhaving great diameter of armature, these values are often\\nexceeded.\\nThe value of 4 depends upon the size of the machine,\\nand the permeability of the metal of its frame. To get a\\nlarge and economical (ft the metal parts of the field magnets\\nare designed to have a very low magnetic reluctance. The\\nair-gap between the pole pieces and the armature, and the\\nspace occupied by the revolving inductors, are each made\\nsmall. The armature inductors are wound upon an iron\\ncore of low magnetic reluctance. These cores are fre-\\nquently slotted and the windings laid in the slots. Besides\\nreducing, to a certain extent, the magnetic reluctance by\\nthis construction, a good mechanical means is furnished\\nfor driving and protecting the inductors. Wires wound on\\nthe exterior of a plain cylinder, or smooth core, under the\\ninfluence of high speeds and the magnetic drag which\\nthey experience have a serious tendency to rub one an-\\nother, and chafe the insulation to its final destruction.\\nThe armatures having slotted cores, which are also called\\ntoothed core armatures, are to be recommended for gene-\\nrators that will be obliged to work under wide variations of\\nload. They cost more to build than smooth-core arma-\\ntures.\\nThe numbers of inductors 5 on an armature can be in-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0049.jp2"}, "50": {"fulltext": "38\\nDYNAMO ELECTRIC MACHINERY.\\ncreased by decreasing the size of the wire. Sufficient\\ncross-section must, however, be left in the inductors to\\ncarry the maximum current of the machine without causing\\na heating of the armature to such a point as to endanger\\nthe insulation. Good practice calls for from 400 to 800\\ncircular mils cross-section of armature conductor per am-\\npere. The smaller values are for intermittently acting\\nmachines elevator motors for example, The larger\\nvalues are for machines that run continuously, such as\\ncentral-station generators.\\n34. Eddy or Foucault Currents in Armature Cores.\\nIt is evident that an imaginary axial lamina of the iron core\\nof an armature is a conductor moving in a field, and there-\\nfore has in it an induced E.M.F. Since this lamina in it-\\nFig. 18.\\nself forms a closed circuit, currents, called Foucault ox eddy\\ncurrents, will flow in it, Fig. 18, and their energy will\\nappear in the form of heat, which will produce an undue\\nelevation of temperature of the armature. To avoid this\\nthe iron of the core is laminated at right angles to the axis\\nof revolution, and the laminae are insulated from one", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0050.jp2"}, "51": {"fulltext": "ARMATURES. 39\\nanother. The heating due to eddy currents is proportional\\nto the square of the thickness of the disks or laminae.\\nCommercial and mechanical reasons limit the decrease of\\nthickness. In good practice the thickness of armature\\ndisks varies from ,01 to .06.\\nFor insulation between the disks reliance is usually\\nplaced on the iron oxid that forms on them during their\\nmanufacture. Generally every six disks or so a further\\ninsulation is interposed by the use of shellac, japan, or\\npaper. Milling slots in laminated armature cores after set-\\nting up causes burrs. These bridge the insulation between\\nthe disks, and militate against the advantages sought after\\nby lamination. For small armatures the disks are punched\\nwhole from sheet -iron, with the teeth and holes for the\\nshaft. These punchings are assembled on the shaft, and\\nheld in place by brass collars set down on either side of the\\npile by nuts on the shaft or by similar devices. In large\\nmachines, parts or segments of the whole periphery are\\npunched separately, and these are assembled with joints\\nstaggered. These large laminae are not directly attached\\nto the shaft, but are mounted upon a spider, which in turn\\nis connected with the shaft. A complete spider and core\\nis shown in Fig. 19.\\nIn large armatures it is usual to make ducts or venti-\\nlating passages in the core by occasionally separating the\\ndisks by the interposition of blocks of insulating material.\\nSuch ventilation carries off the heat, and lessens the rise of\\ntemperature of the armature when in operation.\\n35. Rating of Machines. The American Institute of\\nElectrical Engineers recommends that all electrical and\\nmechanical power be expressed, unless otherwise specified,", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0051.jp2"}, "52": {"fulltext": "40 DYNAMO ELECTRIC MACHINERY.\\nFig- 19.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0052.jp2"}, "53": {"fulltext": "ARMATURES. 41\\nin kilowatts that the full-load current of an electric gene-\\nrator be that current which, with the rated full-load volt-\\nage, gives the rated kilowatts that all guaranties on heat-\\ning, regulation, and sparking should apply to the rated\\nload, except where expressly specified otherwise that\\ndirect current generators should be able to stand an over-\\nload of 25 per cent for one-half hour without an increase\\nof temperature elevation exceeding 15 C. above that\\nspecified for full load and that direct current motors\\nshould, in addition, be able to stand an overload of 50 per\\ncent for one minute.\\nConcerning the normal permissible elevation of tempera-\\nture the following statements are taken from articles 25 to\\n31 of the Institute s Standardization Report\\nUnder regular service conditions, the temperature of\\nelectrical machinery should never be allowed to remain at\\na point at which permanent deterioration of its insulating\\nmaterial takes place.\\nThe rise of temperature should be referred to the stan-\\ndard conditions of a room temperature of 25 C, a baro-\\nmetric pressure of 760 mm. and normal conditions of\\nventilation that is, the apparatus under test should neither\\nbe exposed to draught nor inclosed, except where ex-\\npressly specified.\\nIf the room temperature during the test differs from\\n2 5 C, the observed rise of temperature should be cor-\\nrected by 1 per cent for each degree C. Thus, with a\\nroom temperature of 35 C, the observed rise of tem-\\nperature has to be decreased by 5 per cent, and with\\na room temperature of 15 C, the observed rise of tem-\\nperature has to the increased by 5 per cent. The\\nthermometer indicating the room temperature should", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0053.jp2"}, "54": {"fulltext": "42 DYNAMO ELECTRIC MACHINERY.\\nbe screened from thermal radiation emitted by heated\\nbodies, or from draughts of air. When it is impracti-\\ncable to secure normal conditions of ventilation on ac-\\ncount of an adjacent engine, or othSr sources of heat, the\\nthermometer for measuring the air temperature should be\\nplaced so as fairly to indicate the temperature which the\\nmachine would have if it were idle, in order that the rise of\\ntemperature determined shall be that caused by the opera-\\ntion of the machine.\\nThe temperature should be measured after a run of\\nsufficient duration to reach practical constancy. This is\\nusually from 6 to 1 8 hours, according to the size and con-\\nstruction of the apparatus. It is permissible, however, to\\nshorten the time of the test by running a lesser time on an\\noverload in current and voltage, then reducing the load to\\nnormal, and maintaining it thus until the temperature has\\nbecome constant.\\nIn apparatus intended for intermittent service, as rail-\\nway motors, starting rheostats, etc., the rise of temperature\\nshould be measured after a shorter time, depending upon\\nthe nature of the service, and should be specified.\\nIn apparatus built for conditions of limited space, as\\nrailway motors, a higher rise of temperature must be\\nallowed.\\nIn electrical conductors, the rise of temperature should\\nbe determined by their increase of resistance. For this\\npurpose the resistance may be measured either by galva-\\nnometer test or by drop-of -potential method. A temperature\\ncoefficient of 0.4 per cent per degree C. may be assumed\\nfor copper. Temperature elevations measured in this way\\nare usually in excess of temperature elevations measured\\nby thermometers.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0054.jp2"}, "55": {"fulltext": "ARMATURES.\\n43\\nIt is recommended that the following maximum values\\nof temperature elevation should not be exceeded\\nCOMMUTATING MACHINES.\\nField and armature by resistance, 50 C.\\nCommutator and brushes by thermometer, 55 C.\\nBearings and other parts of machine, by thermometer, 40 C.\\nWhere a thermometer, applied to a coil or winding, in-\\ndicates a higher temperature elevation than that shown by\\nresistance measurement, the thermometer indication should\\nbe accepted. In using the thermometer, care should be\\ntaken so to protect its bulb as to prevent radiation from it,\\nand, at the same time, not to interfere seriously with the\\nnormal radiation from the part to which it is applied.\\nIn the case of apparatus intended for intermittent ser-\\nvice, the temperature elevation, which is attained at the end\\nof the period corresponding to\\nthe term of full load, should\\nnot exceed 50 C. by resistance\\nin electric circuits. In the case\\nof railway, crane, and elevator\\nmotors, the conditions of ser-\\nvice are necessarily so varied\\nthat no specific period corre-\\nsponding to the full-load term\\ncan be stated.\\nThe manner in which temper-\\nature elevation is affected by size of load and duration of\\nfull load is shown in Figs. 20 and 21. The temperature\\nof stationary surfaces rises about 8o\u00c2\u00b0 when radiating one\\nwatt per square inch. The rise is but 15 to 20 when the\\n300\\n1 1 1 1 1 III 1 1\\n.0.\\n8JSE IN TEMPERATURE CURVE\\n300 K. W. SIZE 280\\nDIRECT DYNAMO\\nRUN LONG ENOUGH ATEACH LOAD TO\\nATTAIN A CONSTANT TEMPERATURE\\nCROCKER-WHEELER ELECTRIC CO.,\\nAMPERE, N. J.\\n100\\ns\\nz\\ns\\nL\\nOA\\nIN\\nTE\\nRM\\n3 O\\nr FL\\nLL\\nL04\\nD\\n4\\n22\\n1\\nFig. 20.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0055.jp2"}, "56": {"fulltext": "44\\nDYNAMO ELECTRIC MACHINERY.\\nsurface is rotating at 3,000 feet per minute in such a\\nmanner as the surface of an armature rotates, and amounts\\nUi\\nI\\nm\\nTEMPERATURE CURVE\\n300 K. W. SIZE 280\\nDIRECT DYNAMO\\nUNDER CONSTANT FULL LOAD\\nCROCKER-WHEELER ELECTRIC CO.\\nAMPERE, N. J.\\n1-\\n\u00e2\u0096\u00a0w\\n.3\\n-s-\\nTIME IN JHoJuRS\\n421\\n3 4 5\\nFig. 21.\\n8 9 10\\nto but io\u00c2\u00b0 to 12 at a speed of 6,500 feet per minute.\\nWithin limits, the ratio of rise of temperature to radiation\\nper unit surface is linear.\\n36. Definitions Concerning Armature Windings. In\\nsome dynamos the inductors and commutator segments are\\nnot all electrically connected with each other. In such\\ncases the winding is called an open-coil winding. This\\ndefinition must not be made to include the double or mul-\\ntiple windings to be described later, where two or more\\nclosed-coil windings on the same core are not electrically\\nconnected to one another. Fig. 22 shows a primitive open-\\ncoil winding. In this type only those inductors on whose\\ncommutator bars the brushes may for the moment be rest-\\ning are in series with the external circuit. All the other\\ninductors are cut out and idle.\\nOpen-coil windings are used chiefly on arc-lighting dyna-\\nmos, and will be further discussed in a following chap-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0056.jp2"}, "57": {"fulltext": "ARMATURES.\\n45\\nter devoted to such machines. Closed-coil windings are\\nmuch more generally used. In this case all the inductors\\nare engaged all the time, save when short circuited at com-\\nmutation, in adding E.M.F. to the circuit. Although there\\nare many kinds of closed-coil windings, they are all alike\\nin that the inductors form one or more endless circuits\\ncompletely around the armature core.\\nBefore showing some of the many types of closed-coil\\nwinding it will be well to define some of the terms used.\\ntrwvwsAAAA/M\\nFig. 22.\\nBy inductor is meant that part of the winding conductor\\nwhich lies on the face of the armature that sweeps past\\nthe pole pieces, and is that part of the conductor in which\\nE.M.F. is induced. In the following descriptions when\\none inductor is mentioned there may be in reality a num-\\nber of wires and, again, a loop said to be formed by two\\ninductors may be a loop of many turns, but the connec-\\ntions and placing would be the same as if actually there", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0057.jp2"}, "58": {"fulltext": "46 DYNAMO ELECTRIC MACHINERY.\\nwere only one inductor. It simplifies the diagrams to\\ntreat the subject in this manner.\\nThat part of an armature winding which is electrically\\nconnected directly between two consecutive commutator\\nsegments is called a coil.\\nA two-circuit winding is one in which the current, on\\nentering the armature at one brush, finds two paths by\\nwhich it reaches the other brush. Since a closed-coil\\nwinding is endless, there must invariably be two paths\\nwhen two brushes are used.\\nA four-circuit or multi-circuit winding is one in which\\nthe current finds four or more paths through the arma-\\nture. There are at least two circuits for every pair of\\nbrushes used in collecting the current, unless the commu-\\ntator bars are cross-connected, as in Fig. 25.\\nIf a winding is so arranged that one commutator bar\\nunder a brush carries all the current from one side of the\\narmature to that brush, then the winding is said to be\\nsingle. If, however, the windings are so arranged that\\ntwo or more bars convey this current to the brush at once,\\nor if the current is commutated at two or more points on\\nthe contact surface of the brush, then the winding is said\\nto be double or multiple. Triple and quadruple windings\\nare not infrequent on machines which carry very heavy\\ncurrents.\\nA singly-re-entrant winding is one in which, by successive\\nangular advances, all the coils have been laid when an\\nadvance of 360 has been made. To be doubly-re-entrant\\nwound the angular advance between successive coils, in the\\norder of their winding, is doubled and the whole winding\\nis not complete until the armature has been gone around,\\nangularly, twice, i.e., through an advance of 720 On the", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0058.jp2"}, "59": {"fulltext": "ARMATURES.\\n47\\nsecond time around the coils fill up the interstices left by\\nthe doubled pitch of the first round. Triply and quadruply\\nre-entrant windings are used. In these the circuit passes\\naround the armature three or four times. Any closed-coil\\nwinding, single or multiple, may be singly or multiply re-\\nentrant, the re-entrancy being reckoned as great as that of\\nany single winding on the armature.\\nThe two principal types of closed-coil armatures are\\nthe gramme or ring armature, and the drum.\\n37. Ring-Armature Windings. As the name implies,\\nthe ring-armature core consists of an annular ring around\\nwhich the armature conductors are wound in a continuous\\nspiral, or two or more separate but interleaved spirals in\\nmultiple windings. These are tapped off at equal inter-\\nvals to the commutator bars. In ring armatures there is\\nbut one inductor per loop of wire, the return being on the\\ninside of the ring where there is no magnetic flux. This\\nwinding, though less generally used than the drum winding\\nis simpler and much more easily illustrated, and will be\\ntreated first.\\ns\\nFig. 23. Fig. 24.\\nFig. 23 shows the simplest of all dynamo armature\\nwindings. It is a bipolar, singly-re-entrant, two-circuit,\\nsingle winding.\\nFig. 24 shows a four-pole, four-circuit, singly-re-entrant,", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0059.jp2"}, "60": {"fulltext": "4 8\\nDYNAMO ELECTRIC MACHINERY.\\nsingle winding. The number of coils should be a multiple\\nof the number of poles to electrically preserve a balance in\\nthe four branches or circuits.\\nFig. 25 is the same as Fig. 24 save that the commutator\\nbars are cross-connected. The current that would flow\\nout of two brushes in the previous case, now flows out of\\none brush. This form is seldom used, since it reduces by\\nhalf the brush contact surface, and thus doubles the heat\\nFig. 25.\\nloss in the transition of the current from the commutator\\nto the brush.\\nFig. 26 shows a four-pole four-circuit singly-re-entrant,\\nsingle winding, where only half as many bars are used as\\nthere are coils. A disadvantage is that coils of considerable\\ndifference of pressure are adjacent, thus increasing the\\ndifficulty of properly insulating them. Ordinarily, if it be\\ndesired to halve the number of bars, it is better to unite\\ntwo adjacent coils in series, and treat them as one. But\\nif the magnetic distribution be uniform, this method of\\nconnecting two coils that are in different parts of the field", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0060.jp2"}, "61": {"fulltext": "ARMATURES.\\n49\\nin series averages up the inequalities and facilitates spark-\\nless commutation.\\nFig. 27 shows a bipolar, two-circuit, singly-re-entrant,\\ndouble winding. The advantages of the double winding\\nare the current is commutated\\nat two points of the bearing-sur-\\nface of the brush, and therefore is\\nonly half as heavy at any one point\\nas when only a single winding is\\nused and the successive bars of\\none winding are separated by the\\nwidth of one bar plus two insula-\\ntions, thus making the short cir-\\ncuiting of a coil by dirt, arc, or\\ninjury very unlikely.\\nIn multipolar windings a distinc-\\ntion is made between the short-\\nconnection and the long-connection types. In the\\nshort-connection type coils in adjacent fields are connected\\nin series, while in the long-con-\\nnection type coils twice as far\\napart are connected together.\\nFig. 28 shows a long-connec-\\ntion, two-circuit, four-pole single\\nwinding. Here only slight dif-\\nferences of potential exist be-\\ntween contiguous coils.\\nFig. 29 represents a ten-pole,\\nlong-connection, two-circuit, sin-\\ngle winding. In these long-con-\\nnection types, which are all more or less highly re-entrant,\\nsmall mention is made of the re-entrancy. Strictly accord-\\nFig. 27.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0061.jp2"}, "62": {"fulltext": "So\\nDYNAMO ELECTRIC MACHINERY.\\ning to definition, the winding in Fig. 29 is re-entrant nine\\ntimes.\\nFig. 30 is a four-\\npole, short -connection,\\ntwo-circuit, single wind-\\ning. Besides the com-\\nplication of the wind-\\nings, this form as well\\nas all other short-con-\\nnection windings, is\\nopen to the objection\\nthat the contiguous\\ncoils have, periodically,\\nthe full E.M.F. of the\\nmachine between them,\\nmaking heavy insulation necessary.\\nFig. 31 gives a four-pole, two-circuit double-wound\\nFig. 30.\\narmature, and Fig. 32 gives a similar winding for a six-\\npole machine.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0062.jp2"}, "63": {"fulltext": "ARMATURES.\\nSI\\n38. Drum Armature Windings. Windings for drum\\narmatures are more varied and more complex than those\\nfor ring armatures, and are much harder to portray dia-\\ngrammatically. But few will be shown.\\nThe most simple of these windings is shown in Fig. 33.\\nThe diagram shows the drum and inductors in section,\\nwith the connections of the commutator end in full lines\\nand those of the back (pulley) end in dotted lines. Those\\ninductors marked with a are supposed to carry a current\\nin the direction from the observer into the paper, and\\nFig. 32. Fig. 33.\\nthose marked with a are supposed to carry a current from\\nthe page to the observer. Those not marked are parts of\\ncoils short-circuited by the brushes. This winding was\\ndevised by von Hefner-Alteneck, and may be used on any\\nbipolar armature having half as many commutator bars as\\nslots, or, if it be smooth core, as many bars as coils. If n\\nbe the number of bars and 2n the number of slots, then\\nthe wire is started at bar 1, passed back through slot 1,\\nacross the pulley end to slot n (or sometimes 71 2, in the", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0063.jp2"}, "64": {"fulltext": "52\\nDYNAMO ELECTRIC MACHINERY.\\nfigure n 8). It is then brought forward through slot n,\\nand attached to bar 2. From bar 2 it passes back through\\nslot 3, across the back end and forward through slot n 2\\nand connects to bar 3. Thus passing back through the\\nodd-numbered slots and forward through the even-num-\\nbered slots, coils can be made to fill the 211 slots and\\neach can be attached to its own commutator bars.\\nFig. 34 is very similar to the last, save that the wires\\nare laid two layers deep, thus allowing the conductor that\\npassed through slot 1 to return\\nthrough slot n 1 which is\\ndiametrically opposite. Both\\nthis winding and the last are\\nclassed as two-circuit single\\nwindings.\\nIn a bipolar machine a chord-\\nwound drum armature is one in\\nwhich the two inductors of one\\nloop are appreciably less than\\n180 apart, so that the wire at\\nH M the back end is a chord rather\\nthan a diameter of the circle of the drum. The advan-\\ntages of this winding are that, on a given drum, it de-\\ncreases the total length of wire necessary to give a definite\\nnumber of inductors, and that it reduces the bunching and\\noverlapping of the wires at the pulley end of the drum.\\nThe disadvantage is that it is impossible to secure a per-\\nfectly electrically balanced winding by this method. This\\nobjection does not hold in the case of multipolar gene-\\nrators, hence all multipolar drums are chord wound.\\nIn the following figures the numbered radial lines will\\nrepresent armature inductors, the lines inside of them will", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0064.jp2"}, "65": {"fulltext": "ARMATURES.\\nS3\\nrepresent their connections to the commutator segments,\\nand the lines outside of them will represent the cross\\nconnections between inductors at the pulley end. The\\nbrushes are placed in-\\nside the commutator\\nfor convenience and\\nclearness.\\nFig. 35 represents a\\nsix-circuit, single wind-\\ning with 80 inductors\\nand 40 segments. In\\npractice the inductors,\\ninstead of all lying be-\\nside each other, would\\nprobably be wound one\\non top of another in\\none slot.\\nFig. 36 shows a rather simple single winding. Although\\nit is four pole it is but\\n.5\\ntwo circuit, in which it\\nresembles Fig. 37, which\\nis, however, a triple wind-\\ning.\\nFig- 38 gives a six-\\npole, two circuit, double\\nwinding.\\nIn winding armatures,\\ndouble or triple cotton in-\\nsulated copper wire is\\ngenerally used. Care\\nFig# 36# must be taken to well in-\\nsulate the wires, both from each other and from the core.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0065.jp2"}, "66": {"fulltext": "54\\nDYNAMO ELECTRIC MACHINERY.\\nMany of these styles of winding create very complex\\nmasses of wire on the\\nends of the drum, and\\ngreat care must be ex-\\nercised both in regard to\\ninsulating and fastening\\nat these points, so that\\nthe movement of the\\nwires under the influence\\nof the magnetic drag\\nmay not chafe the insu-\\nlation and short-circuit\\nthe conductors. Mica is\\nthe best insulator, and is\\nused where flat sheets are needed but its great cost, and\\nthe difficulty of manipulating it, result in the extensive use\\nof canvas, oiled paper, rubber tape, vulcanized fiber, and\\nmany patented manufac-\\ntured insulators. Much\\nreliance is placed upon\\nthe liberal use of japan\\nand shellac, especially in\\nconjunction with canvas.\\nWhere very large\\nwires are used on the\\nsurface of an armature,\\neddy currents are set up\\nin them by reason of one\\nside of the wire being\\nin a stronger field than Flg 38\\nthe other. To avoid this a number of smaller insulated\\nwires are wound in parallel, to take the place of the larger", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0066.jp2"}, "67": {"fulltext": "ARMATURES. 55\\none, or what is more economical of space, thin copper bars\\nset edgewise take the place of the round wire.\\nIn the winding of multipolar armatures it is possible to\\nuse formed coih r, which are wound on a separate collapsible\\nforming block, and are afterward applied to the core. This\\nmethod is advantageous in that better insulation can be as-\\nsured, and damaged or burned-out coils can be replaced\\nwithout disturbing all of the windings. Fig. 39 shows a\\nGeneral Electric Company s formed coil, and Fig. 40 some\\nof the Crocker Wheeler coils.\\nFig. 39.\\nAll armatures, whether wound with wire, or formed coils,\\nor shaped conductors, must be banded around to prevent\\ndislodgement of the conductors under influence of cen-\\ntrifugal action. The wire used for this purpose is gener-\\nally of hard-drawn brass or of phospher bronze, and on\\nrailway motors of steel. It is wound over insulating strips\\nforming a band of several turns. The completed turns\\nare often sweated together with solder.\\nMany manufacturers punch a small recess in each side\\nof the teeth near the face. A strip of maple wood is fitted", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0067.jp2"}, "68": {"fulltext": "56\\nDYNAMO ELECTRIC MACHINERY\\nbx", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0068.jp2"}, "69": {"fulltext": "ARMATURES.\\n57\\nFig. 41.\\nFig. 42.\\ninto the recesses, and acts like a cover to the slot, firmly-\\nholding the windings in place, and presenting a neat ap-\\npearance.\\nFigs. 41, 42, 43 show respectively a core, a partially\\nwound, and a completed General Electric Company s arma-\\nture. Figs. 44 and 45 show small Westinghouse types.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0069.jp2"}, "70": {"fulltext": "58\\nDYNAMO ELECTRIC MACHINERY.\\nFig. 43.\\nFig. 44.\\nFig. 45-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0070.jp2"}, "71": {"fulltext": "ARMATURES. 59\\n39. Commutators. The segments or bars of a commu-\\ntator are always of drop-forged, or hard-drawn copper.\\nThe insulation between them is always of mica. There\\nare various grades of mica and for insulating purposes the\\namber-colored mica, which must be free from iron, is to be\\npreferred. Besides being a good insulator, amber mica has\\nthe additional advantage that it wears at the same rate as\\ncopper thus after long use it leaves neither elevations nor\\ndepressions on the commutator surface.\\nIn fastening the bars considerable ingenuity is displayed\\nfor they must not displace themselves with reference to\\nthe windings, neither must one bar lift so as to be above\\nthe level of its neighbors. If the latter occurs, then, when\\nthe bar comes under a brush, it will lift it and as the\\nhigh spot moves out from under the brush the contact is\\nbroken until the spring can reseat the brush. This causes\\nexcessive wear and destructive sparking.\\nAfter a commutator has been for a time in use, it becomes\\ngrooved and pitted, a condition which causes further spark-\\ning and wear, and the commutator must be turned down\\nagain to a true surface. The design of a commutator\\nshould allow of good operation after it has been subjected\\nto this treatment.\\nMechanical friction and the electrical losses that accom-\\npany commutation will raise the temperature of the com-\\nmutator about 5 C. above that of the armature. To\\nsecure successful operation a commutator must be de-\\nsigned with a sufficient number of bars, so that the differ-\\nence of potential between two adjacent bars shall not\\nexceed 10 volts. This would mean that a.ioo-volt bi-\\npolar machine should have at least 20 bars. The potential\\nbetween the brushes or around half the commutator is 100", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0071.jp2"}, "72": {"fulltext": "60 DYNAMO ELECTRIC MACHINERY.\\nvolts, hence half the commutator must have 10 bars.\\nThere is no general rule for the length of a commutator\\nbar, but one may roughly say that there should be at least\\none inch per ioo amperes.\\nCommutators should be designed so as to expose a suffi-\\ncient area to radiate the heat which is communicated to\\nthem. Except in the case of some special commutators,\\nwhich are supplied with cooling devices, at a peripheral\\nspeed of 2,500 feet per minute, the radiation of one watt\\nper square inch of peripheral radiating surface will re-\\nsult in a rise of temperature of 20 C. The permissible\\nrise of 55 C, therefore, allows a radiation of 2.75 watts\\nper square inch. The heat to be radiated is due to the fol-\\nlowing causes\\na. Friction between the brushes and the commutator\\nbars. This is equal to J times the product of\\nthe following quantities The radius of the commutator in\\nfeet, the speed in revolutions per minute, the coefficient\\nof friction between the brushes and the commutator (0.3\\nfor carbon brushes and 0.25 for copper brushes), and the\\nsum of the pressures of all the brushes upon the commuta-\\ntor. This latter should amount to 1.25 lbs. per square inch\\nof rubbing surface. Copper brushes permit 200 amperes\\nper square inch of rubbing surface, and carbon brushes\\n40 amperes.\\nb. The contact resistance between the brushes and the\\ncommutator. As there is always a drop of about one volt\\nat each point of contact, and as there is a drop at both the\\npositive and negative terminals, the watts represented by\\nthese contact resistances are numerically equal to twice the\\ncurrent of the machine.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0072.jp2"}, "73": {"fulltext": "ARMATURES. 6l\\nc. The energy represented in the sparking at the brushes\\nand the heat due to waste currents in the short-circuited\\nsegments. These two losses cannot be accurately calcu-\\nlated, but may be estimated as equal to about 6 per cent of\\nthe total commutator loss.\\nOuter mica cooes tt^^fe^^r*i. /fflL jV\\nInner-\\ntttica collar- vjndler- segment s\\nClamping r\\\\r\\\\Q\u00e2\u0080\u0094\\nneU\\nFig. 46 gives a broken-away view of a General Electric\\ncommutator, showing the methods of attachment and insu-\\nlation.\\n40. Collecting Devices. These consist of the brushes,\\nthe brush holders, and the rockers.\\nBrushes for high potential machines are of carbon. Car-\\nbon against copper causes less wear than copper against cop-\\nper, and further, the greater resistance of a carbon brush\\nresults in less sparking when it bridges two commutator bars\\nthan would the lower resistance of a copper brush. Com-\\nbination brushes of carbon and copper are sometimes used.\\nCarbon brushes are set at an angle generally, though some\\nmakers set them radially and in motors that must be re-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0073.jp2"}, "74": {"fulltext": "62 DYNAMO ELECTRIC MACHINERY.\\nversed, as is the case with railroad and elevator motors,\\nthey are invariably set radially. A surface contact of one\\nsquare inch per 40 amperes is usual for carbon brushes.\\nOn low-potential machines copper brushes, set at an angle\\nof 45 with the tangent to the commutator surface at the\\npoint of contact, are invariably used. This is because there\\nis less natural tendency to spark on low voltages, and be-\\ncause the resistance of carbon\\nbrushes would be too great a\\nfraction of the whole resistance of\\nthe circuit, and cause a wasteful\\ndrop of potential. Copper brushes\\nfjJ^ must have their ends filed to give\\nsufficient surface contact, and this\\nis generally done with the aid of a. jig, illustrated in Fig. 47.\\nThe abrasion of carbon brushes is accomplished by means\\nof glasspaper.\\nBrush holders should permit of a low-resistance contact\\nbetween the brush and the leads, they should provide ad-\\njustment as to position and tension of the brushes, and\\nthey should be arranged so that none of the springs shall\\nget hot and lose temper while in performance of its duties.\\nThe tension on carbon brushes varies from 1 to 10 lbs. per\\nsquare inch of contact surface. The lower limit is to be\\nfound in large central station generators, and the higher\\nlimit in small machines and in motors which are subjected\\nto frequent and sudden strains, as railway motors. The\\ncoefficient of friction between brush carbon and copper\\nvaries from 0.28 to 0.32.\\nFigs. 48 and 49 plainly show a Crocker Wheeler rigging\\nwith parallel-motion brush holders. Fig. 50 shows a form\\nof General Electric holder.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0074.jp2"}, "75": {"fulltext": "ARMATURES\\nFig. 48.\\nQ^\\\\ CLAMPING SCREW\\nADJUSTING\\nSCREW\\nHARD ROLLED COPPER LEAVES", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0075.jp2"}, "76": {"fulltext": "64 DYNAMO ELECTRIC MACHINERY.\\nRockers are rings or attachments carrying the brush\\nholders, and they are mounted concentric with the com-\\nmutator. They are made to give all the brushes of the\\nmachine, or sometimes all the positive brushes or all the\\nnegative brushes at once, a motion around the axis, thus\\nadjusting all brushes by one movement. Fig. 5 1 shows\\nsuch a rocker.\\n41. Shafts, Bearings, and Oilers. Since armature\\nshafts generally have high speeds, and almost always are\\nsubject to sudden large variations of load, the shafts, the\\nx\\nFig. 50.\\nbearings, and the oiling facilities must be well designed.\\nWiener gives the following approximate diameters of steel\\nshafts for drum armatures\\nFor 100 watts I inch,\\nFor 1,000 watts 2 inches,\\nFor 10,000 watts 4! inches,\\nall to be turned down at the bearings.\\nIt is necessary that the bearing-boxes be exactly in line,\\nand a form of self -alignment bearing is frequently used. If\\nundue wear in the bearings occur, the armature is apt to", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0076.jp2"}, "77": {"fulltext": "ARMATURES.\\n65\\nsag till it strikes a pole piece, which will damage the arma-\\nture. Many machines use ordinary oil cups to secure\\nlubrication, while others make use of some device, as is\\nshown in Fig. 52. The shaft revolves in a cylindrical brass\\nwith a spherical enlargement at its middle which rests upon\\nFig. 51.\\na corresponding spherical bed of Babbit metal. This se-\\ncures self-alignment. Two slots are cut radially in the\\nbrass, and allow two rings to rest upon the shaft. These\\nrings are also of brass, and have an inside diameter slightly\\nlarger than the outside diameter of the brass cylinder.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0077.jp2"}, "78": {"fulltext": "66\\nDYNAMO ELECTRIC MACHINERY.\\nThe pillow block is hollowed away under these rings, the\\nhollows serving as receptacles for the storage of oil. As the\\nFig. 52.\\nshaft revolves, the rings also revolve at such a rate as to\\ncarry a steady stream of oil up into the slots, thereby\\nlubricating the bearing.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0078.jp2"}, "79": {"fulltext": "FIELD MAGNETS.\\n67\\nCHAPTER IV.\\nFIELD MAGNETS.\\n42. Parts of Field Magnets. The parts of a dynamo,\\nexclusive of the armature, which make up the magnetic\\ncircuit, belong to the field magnets. Fig. 53 shows a con-\\nventional bipolar horse-shoe type with the parts plainly\\nmarked. The field cores are the iron centers in the mag-\\nnetizing coils. The yoke connects the cores together at\\none end while the other ends terminate in the pole pieces,\\nFig- 54.\\none being a north magnetic pole, the other a south. The\\nside of the pole piece embracing the armature is styled the\\npole face, and the latter s projecting edges are fittingly\\ncalled the horns. Some dynamos have the magnetizing\\ncoils on the yoke, thus making the latter serve also as\\ncore. In different types different numbers of pieces pre-\\nvail, thus all the parts (save the coils) might be cast in\\none piece or each might be made separately.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0079.jp2"}, "80": {"fulltext": "68 DYNAMO ELECTRIC MACHINERY.\\nIn multipolar machines the designation of the parts is\\nsomewhat different than in the case of bipolar machines.\\nThe particular designation often depends upon the manu-\\nfacturer. Fig. 54 gives the designation used by the\\nCrocker Wheeler Company.\\n43. Magnetic Material. The materials used for field\\nmagnetic circuits are three, cast iron, wrought iron, and\\ncast steel. The selection of material for a given machine\\nis governed by considerations of (a) weight, (b) first cost,\\n(c) economy and satisfactory regulation when in operation.\\nCast iron has the great advantage of cheapness but it is\\npoor magnetically, hence more weight and bulk must be\\nemployed to perform the same service as the magnetically\\nsuperior wrought iron. It costs more in copper to magne-\\ntize a cast-iron core, because more turns will be required,\\nand each turn will be longer than if the core were of better\\nmaterial.\\nWrought iron is the best magnetic material available.\\nIt is used either in forgings, or in the form of plates\\npunched from the sheet. In either form it is expensive but\\nsince less weight in a given machine is necessitated when\\nthis metal is used, it is often chosen where portability\\nis required, as in the case of the marine dynamos, electric\\nrailroad motors, and particularly motors for automobiles.\\nCast steel is intermediate between cast iron and wrought\\niron, both in cost and in magnetic properties, and is much\\nemployed in good practice. The use of different metals in\\ndifferent parts of the frame is very general. For instance,\\na cast-iron yoke is used with cast-steel cores and pole\\npieces, or a cast-iron or steel yoke is used with wrought-\\niron cores and pole pieces.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0080.jp2"}, "81": {"fulltext": "FIELD MAGNETS. 69\\n44. Shape of Field Magnets There is a great vari-\\nety of shapes of field magnets. Formerly each manufac-\\nturer had a type peculiarly his own, and this led to many\\nforms, some of little merit. These freak types are now\\ndisappearing, and a few general types are adopted more or\\nless by all makers. In all forms, however, the polar span,\\nor part of the armature circle that is covered by pole faces,\\nis from 65 per cent to 75 per cent, or from 234 to 270\\nIn general a small number of poles in the field magnets re-\\nquires less copper in the exciting coil than does a larger\\nnumber, and also the fields can be excited more economi-\\ncally. But in large bipolar machines successful operation\\nunder varying loads requires a large air gap between the\\npole face and the armature. This increases the magnetic\\nreluctance and the energy necessary for excitation. Multi-\\npolar machines do not require so large an air gap. Further-\\nmore, increasing the number of poles gives the mechanical\\nadvantage of allowing a lower armature speed without low-\\nering the potential of the output. Multipolar machines\\nwill run cooler than bipolars of the same economy of\\noperation.\\nSpeaking generally, though it is by no means a rule,\\nbipolar fields are used up to about 10 k.w., four-pole fields\\nfrom 10 k.w. to 100 k.w., six-pole fields from 100 k.w. to\\n300 k.w., and beyond that point eight or more poles are\\ngenerally used.\\n45. Methods of Excitation of Fields. Dynamos are\\nclassified according to the five methods of exciting the\\nfields of the machine. They are the Magneto, the\\nSeparately Excited, the Shunt Wound, the Series Wound,\\nand the Compound Wound.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0081.jp2"}, "82": {"fulltext": "7o\\nDYNAMO ELECTRIC MACHINERY.\\nThe magneto generator, Fig. 55, is one in which the\\nfield is a permanent steel magnet, generally of horse-shoe\\ntype.\\nThe separately excited dynamo, Fig. 56, has, as its\\nMAGNETO DYNAMO\\nFig. 55-\\nSEPARATELY EXCITED DYNAMO\\nFig. 56.\\nname implies, its field coils traversed by a current other\\nthan that produced by the machine. Alternating current\\nmachines are nearly always of this type.\\nThe shunt-wound machine, Fig. 5 7, has a large number\\nof turns of fine wire wound on its core, and the ends are\\nD\\n1\\nj 1\\nn\\nD\\n8HUNT WOUND\\nDYNAMO\\nFig. 57.\\nSERIES WOUND\\nDYNAMO\\nFig. 58.\\nconnected to the terminals of the machine, thus being in\\nshunt with the outside circuit. The ampere turns requisite\\nfor excitation are obtained by passing a small number of\\namperes through a large number of turns.\\nThe series-wound generator, Fig. 58, has all the cur-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0082.jp2"}, "83": {"fulltext": "FIELD MAGNETS.\\nn\\nrent that is produced by the armature passed through\\nlarge conductors wound with fewer turns around the cores.\\nThe exciting coils are then in series with the external cir-\\ncuit. The ampere turns required for excitation are ob-\\ntained by passing a large current through a small number\\nof turns.\\nThe compound machine, Fig. 59, is one in which there\\nare both shunt and series coils on the field magnets. This\\nmethod of winding is used for purposes of regulation under\\nvarying loads, as will be explained later. Compound wind-\\nings are of two classes, the long shunt and the short shunt.\\nIn the former, the current used in the shunt windings is\\nj\\nl\\ns\\nI\\nI\\nf~\\nCOMPOUND WOUND\\nDYNAMO LONG SHUNT\\nFig. 59.\\nCOMPOUND WOUND\\nDYNAMO SHORT SHUNT\\nFig. 60.\\nalso passed through the field windings along with the main\\ncurrent. In the latter, the current from the shunt coils\\npasses directly back to the armature, avoiding the series\\nturns. Figs. 59 and 60 clearly show the two methods.\\nThe short shunt is generally preferred.\\n46. Field Coils. The coils of a dynamo must, without\\nundue elevation of temperature, supply sufficient ampere\\nturns to give the required excitation. This temperature\\nrise will not be excessive when about o. 3 5 watts are radiated\\nper square inch of outer surface of the coil. If no account\\nbe taken of the ends of the pole and coil, 0.6 watt may be", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0083.jp2"}, "84": {"fulltext": "72\\nDYNAMO ELECTRIC MACHINERY.\\nallowed per square inch. The field coils have no ventila-\\ntion due to their own motion as have armatures, hence\\nabout iooo circular mils per ampere must be allowed in\\nthe wire which composes such coils. The cost of copper\\nis needlessly increased, if more than the necessary cross-\\nsection be allowed.\\nFig. 61.\\nField coils are usually wound on brass or iron spools,\\nshaped to slip over the cores. Sometimes, especially in the\\ncase of small machines, the coils are wound on frames,\\nwhich can be collapsed and removed. The coils of series\\nmachines and the series coils of compound machines are", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0084.jp2"}, "85": {"fulltext": "FIELD MAGNETS.\\n73\\noften wound with copper ribbon instead of wire, or are even\\nmade up of forged copper conductors, having a rectangular\\ncross-section. This is because the heavy currents require\\nsuch large cross-section of conductor that if made of wire\\nmuch space would be lost between the wires. The rear\\ncoil in Fig. 61 is a series coil of shaped conductors. This\\nfigure shows both the shunt and the series coil, as wound\\nby the Westinghouse Company, for a compound multipolar\\nrailway generator. The binding which is seen on the shunt\\ncoils in both illustrations should not be mistaken for the\\nwires of these coils. Field coils are wound with double\\ncotton-covered copper wire. Further insulation between\\ncoil and core, and between series and shunt coils, is effected\\nby the use of fiber, fuller board, and mica.\\n47. Magnetic Leakage. Since air is not an insulator\\nof magnetism, but is simply much less permeable than\\niron, it is evident that some of\\nthe lines of force generated by\\nthe field coils will not follow\\naround the desired path through\\npole pieces and armature, but will\\ntake a path through the air and\\nbe of no utility in creating E.M.F.\\nin the revolving armature. Fig.\\n62 roughly represents some of\\nthe paths such lines may take.\\nIf f t be the total flux caused by the field coils and a be\\nthe flux that passes through the armature, then the coeffi-\\ncient of magnetic leakage,\\nL\\nPa\\nand is always greater than unity.\\nFig. 62.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0085.jp2"}, "86": {"fulltext": "74\\nDYNAMO ELECTRIC MACHINERY.\\nIn practice L varies from 1.25 to 1.4 in single horse-\\nshoe fields, and in the Edison type of inverted horse-shoe\\nand in double horse-shoe fields it varies from 1.5 to 1.75.\\nIn multipolar machines X. varies from 1.1 to 1.5.\\nTo find the coefficient of magnetic leakage of small or\\nmoderate sized machines proceed as follows\\nArrange the field-coils for separate excitation by a cur-\\nrent that can be conveniently commutated. Suppose the\\nmachine to have a field of the double horse-shoe type, as in\\nFig. 63. Take a few turns of fine insulated wire about\\nthe middle of one coil, as c, d, and connect the ends to a\\nFig. 63.\\nballistic galvanometer of low sensioility. A low-reading\\nWeston voltmeter will answer. Suddenly commutate\\nthe current in the field coils. The change in direction of the\\nflux in the core, from to will induce E.M.F. in the\\ntest coil, which will give a throw to the voltmeter needle.\\nThe deflection is directly proportional to the flux in the\\ncore. Repeat with the other coil, and the sum of the de-\\nflections obtained from cd and ef is directly proportional\\nto the total flux produced j t Now make a test coil of the\\nsame number of turns and of the same resistance about\\nthe armature, in such a position ab that it includes the area", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0086.jp2"}, "87": {"fulltext": "FIELD MAGNETS. 75\\nof the armature that is cut by the greatest number of lines\\nof force. Upon commutating tic e current a throw of the\\nneedle will result, which is propational to the flux in the\\narmature a Hence the coefficient of magnetic leakage,\\n__ f t _ defl. at cd defl. at ef\\na deflection at armature\\nThe exciting current must remain constant during the\\ninvestigation.\\nThe location of the different leakage paths may be found\\nby using test coils on different parts of the frame. The\\ndifference between the throws observed at any two places\\nis a measure of the leakage between those two places.\\nClearly the number of lines choosing paths through the\\nair will decrease as the permeability of the iron circuit\\nincreases. An increase in the reluctance of the main\\nmagnetic circuit will increase the leakage loss.\\nArmature cores vary in permeability under varying con-\\nditions of load. As the load increases, this change pro-\\nduces an increase in the reluctance of the main magnetic\\ncircuit. This results in an increase of the loss by leakage.\\nThe coefficient of magnetic leakage is, therefore, different\\nwith different loads.\\n48. Pole Pieces and Shoes. In general practice the\\nfield cores and the frame of a generator are worked at a\\nflux density of at least 15,000 lines per sq. cm.\\nThis is too high a value to use in the air gap. Therefore\\npole shoes are put on the ends of the pole pieces to dis-\\ntribute this flux over a wider area where it has to pass\\nthrough the air, and to thus decrease the total reluctance\\nof the magnetic circuit.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0087.jp2"}, "88": {"fulltext": "j6 DYNAMO ELECTRIC MACHINERY.\\n49. Effect of Joints in the Magnetic Circuit. Since no\\ntwo pieces of metal can be put together with a perfect\\njoint, there is always an increase of reluctance in a mag-\\nnetic circuit when a joint is introduced therein. Professor\\nEwing found by experiment that at low magnetizations\\n(3C 7.5) the increase of reluctance of a certain bar of\\niron due to a joint was above 20 per cent, and that for\\nhigh magnetizations (3C 70) the loss due to one joint was\\nless than 5 per cent. The difference is probably due to\\nthe fact that the pieces under strong magnetizations attract\\nthemselves so powerfully as to make a more perfect joint.\\nEwing also found that a single cut in a bar acted upon the\\nreluctance of the bar as though the length of the bar had\\nbeen increased by amounts given in the following table\\nForX 7.5 15 30 50 70\\nEquivalent length of 1 cut\\nin cms. of iron 4 2.53 1.10 0.43 0.22", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0088.jp2"}, "89": {"fulltext": "OPERATION OF ARMATURES. JJ\\nCHAPTER V.\\nOPERATION OF ARMATURES\\n50. Process of Commutation. The simple process of\\ncommutation as described in 30 is attended with some\\ndifficulties in practice. Consider one coil of a plain ring\\narmature with the commutator bars attached thereto as in\\nFig. 64. In position A, when the brush is on only one of\\nthe bars in question, the action of the other coils of the\\narmature will be to force current in this one coil in the\\ndirection indicated by the arrow. B is considered to be\\nthe positive brush. In position D, when the brush has\\npassed over to the other bar entirely, the direction of the\\ncurrent in this coil is in the other direction. Now this\\nchange of direction must occur when the coil is in a weak\\nfield, for it is observed that the coil is short circuited while\\nin position C, the circuit being completed through the coil,\\nthe bars and the brush spanning the mica insulation at o.\\nIf now at this moment the coil should be in a strong field,\\nand should be cutting many lines of force, too large an", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0089.jp2"}, "90": {"fulltext": "78\\nDYNAMO ELECTRIC MACHINERY.\\nE.M.F. would be produced, and as the resistance of the\\ncircuit indicated is very low, an excessively strong current\\nmight flow. When the brush slips past o the circuit is\\nbroken, and a more or less serious sparking occurs accord-\\ning to the strength of the current flowing at the instant of\\nbreak. Commutation must then be effected when the coil\\nis in such a position as not to cut many lines of force. It\\nfollows that every commutating machine must have at\\nleast two places where the effective field has a zero value.\\nFig. 65 gives a rectified curve of the magnetic distribution\\nFig. 65.\\nunder the pole pieces and around the armature of a well-\\ndesigned bipolar machine, the ordinates of the curve giving\\nthe flux density in the air gap.\\nThe neutral plane is a plane passed through the axis of\\nthe armature and a point in the field immediately surround-\\ning the armature, where the inductively effective com-\\nponent has a zero value. The coil in position C, Fig. 64\\nis supposed to be in the neutral plane.\\nThe commutating plane is a plane passed through the axis\\nof the armature and through the points of contact of the\\nbrushes. The segments are supposed to be connected with\\nparts of the armature windings lying on the same radius.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0090.jp2"}, "91": {"fulltext": "OPERATION OF ARMATURES. 79\\n51. Influence of Self-induction of the Commutated\\nCoil. When the coil in Fig. 64 is in position A the cur-\\nrent flowing in it produces magnetic flux in the ring inde-\\npendent of any inductive action of the field magnets of the\\ndynamo, and links the flux with itself. When the coil is\\nin position D, there is also a magnetic flux and linkage, but\\nits direction has been changed. Therefore, in passing\\nthrough the position C y the current in the coil and the\\naccompanying flux linked with the coil have decreased to\\nzero, and have afterwards risen in value in the opposite\\ndirection.\\nThis change of flux produces an E.M.F. in the coil inde-\\npendent of any action of the field magnets (see 15). This\\nE.M.F. is called an electromotive force of self-induction and\\ntends to continue the flow of a current which has been\\nstarted, and tends to prevent any increase or decrease in\\nthe strength of the current and to prevent the stopping or\\nstarting of the current. The value of this self -induced\\npressure with a given flow of current varies as the square\\nof the number of turns in the coil, as the cross-section of\\nthe coil, and as the permeance of the magnetic circuit.\\nBecause of self-induction it is evident that, if commutation\\ntake place in the neutral plane, there is a liability that it\\nwill be accompanied by excessive currents in the short-cir-\\ncuited coils and consequently by sparking. This trouble\\nis to be avoided by revolving the plane of commutation\\nabout the shaft of the machine until a sufficiently strong\\nfield acts upon the short-circuited coil to induce an opposing\\nE.M.F. of the same value as the E.M.F. of self-induction.\\nBoth the self-induced E.M.F. and the E.M.F. due to the\\nrotation of the armature vary in magnitude during the\\ntime that a brush is upon two adjacent segments. Their", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0091.jp2"}, "92": {"fulltext": "8o\\nDYNAMO ELECTRIC MACHINERY.\\nmanners of variation need not be alike, and hence it may-\\nbe impossible in some cases to effectively oppose one\\nagainst the other. The\\nobvious remedy is to be\\nsought in more com-\\nmutator segments or a\\nchange of shape of pole\\nshoe.\\n52. Cross-Magnetiz-\\ning Effect of Armature\\nCurrents. Indepen-\\ndent of field magnets\\nthe current flowing in\\nthe armature conductor\\nwill magnetize the ar-\\nmature core. The poles thus produced will be in the\\nplane of commutation. Fig. 66 shows the magnetizing\\neffect of the armature turns\\non a ring armature. Fig.\\n67 shows a cross-section of\\na drum armature and its\\nwindings with the resulting\\nmagnetization.\\nThus, when there is a\\nload on a dynamo and the\\narmature conductors are\\ncarrying a heavy current,\\nthere are two coexistent\\nmagnetic fields. This condition results in a skewing of\\nthe lines of force, as is shown in Fig. 68. As the lines\\nare skewed the neutral plane is shifted. To produce spark-\\nFig. 67.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0092.jp2"}, "93": {"fulltext": "OPERATION OF ARMATURES.\\n8l\\nFig. 68.\\nless commutation the commutating plane must also be\\nshifted. This causes a further skewing of the lines. The\\nlimit of this double interdependent shifting is reached\\nwhen the magnetic lines have\\nbecome so crowded in the\\ntrailing-pole tips that they are\\nalmost insensible to a further\\nshifting of the plane of com-\\nmutation.\\nThis skewing is a source of loss in the operation of a\\ngenerator because it increases the magnetic reluctance in\\ntwo ways, (a) by saturating the iron at the horns, and\\nthus reducing the permeability, and (b) by lengthening the\\npaths, both in air and in iron, that the lines must follow.\\nFig. 69 shows a\\ncurve similar to Fig.\\n65 taken when the gen-\\nerator was under load\\nand the armature was\\ntraversed by a heavy\\ncurrent, the flux being\\ndistorted because of it.\\nIt is evident that the\\nangular displacement of\\nthe neutral plane depends in magnitude upon the relative\\nnumber of armature ampere turns as compared with the ef-\\nfective field ampere turns. The use of a strong field and a\\nlarge air-gap length requires a large number of field ampere\\nturns. Both are much used in practice with great success.\\nFig. 69.\\n53. Demagnetizing Effect of Armature Currents. It\\nhas been shown that it is necessary to have the commu-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0093.jp2"}, "94": {"fulltext": "82\\nDYNAMO ELECTRIC MACHINERY.\\ntating plane in advance of the neutral plane. The angle\\nbetween them is called the angle of lag or lead. If an\\naxial plane be passed through the armature, making with\\nthe neutral plane an angle equal to the angle of lag or lead,\\nbut on the opposite side of the neutral plane from the corn-\\nmutating plane, then the angular space between this plane\\nand the commutating plane is called the double angle of\\nlag or lead. The armature conductors, which create a\\nmagnetism that tends to skew the lines of the field magnets\\nas shown in the last article, are called the cross turns.\\nFig. 70.\\nThey lie outside the double angle of lead. Those armature\\nconductors which lie within the double angle of lead are\\ncalled the back turns, because, when carrying a current,\\ntheir magnetic tendency is to send lines in a direction\\nexactly opposite to the lines of the field magnets. They\\nneutralize in a certain measure the action of the field turns.\\nThis action is clearer shown in Fig. 70, which is a cross-\\nsection of a bipolar drum armature. At a there is a north\\npole due to the back turns which lie in the double angle,\\nand at b there is the corresponding south pole. The effect", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0094.jp2"}, "95": {"fulltext": "OPERATION OF ARMATURES. 83\\nof these poles is to neutralize some of the useful magnetic\\nlines flowing from N to S. At c there is a south pole\\ndue to the remaining or cross armature turns and at d is\\nthe corresponding north pole. These poles skew the lines\\nflowing from N to S. Compensation for back turns is\\neasily calculated, since the number of back turns times\\nthe current in them at any load multiplied by the coeffi-\\ncient of magnetic leakage at that load 47) gives the\\nnumber of additional field ampere turns necessary at that\\nload for compensation.\\n54. Sparking. As shown in 51, sparking can be\\navoided by giving the brushes a lead sufficient to bring the\\ncoils they short circuit into fields sufficiently strong to coun-\\nteract the effects of self-induction. Sparking in the opera-\\ntion of machines is generally due to the misplacement of the\\nbrushes, though sometimes it is due to irregularities of the\\ncommutator surface. A high bar passing from under a\\nbrush will leave the latter suspended in air a moment, which\\nwill break the whole current through\\nthe brush and cause a bad spark or\\narc.\\nA machine may also suffer melting\\nof the commutator bars without any\\nvisible sparking. Suppose a coil of\\nlow resistance to be short circuited\\nby a copper brush as in Fig. 71.\\nWhen the brush is chiefly on one\\nbar, and over-laps the other very\\nslightly, then a very considerable part of the resistance in\\nthe circuit is the transition resistance at the small contact.\\nUnder an E.M.F. of self-induction a current of sufficient", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0095.jp2"}, "96": {"fulltext": "84 DYNAMO ELECTRIC MACHINERY.\\nmagnitude may flow to produce enough heat in the trans-\\nition resistance to melt the surface of the commutator bar.\\nThe E.M.F. may then disappear before the brush leaves\\nthe bar, and there will be no spark visible.\\nSparking may be due to excessive electromotive force\\nbetween the commutator segments undergoing commuta-\\ntion due to the self-induction of the coil and to mutual\\ninduction between it and other coils undergoing commuta-\\ntion at the same time. To be able to determine the value\\nof this induced E.M.F. one must know both the self and\\nmutual inductances, and the time rate of suppression of the\\ncurrent in the coil. Parshall and Hobart state that in\\npractice one may assume that a coil of a single turn when\\ntraversed by one ampere produces and links with itself\\n20 c.g.s. lines per inch net length of armature lamination.\\nFrom this datum one can calculate the values of the self-\\ninductance and mutual inductance.\\nA coil which is undergoing commutation must have its\\ncurrent changed from a maximum value in one direction to\\nzero and from zero to a maximum value in the other direc-\\ntion during the time that the two segments at its ends are\\nconnected through the brush. This time is evidently\\ndependent upon the peripheral speed of the commutator\\nand upon the width of the brush. It is equal to the time\\nthat it takes a point of the insulation between the seg-\\nments to pass over the breadth of the brush that is, the\\ntime in seconds is equal to the breadth of the brush in\\ninches divided by the peripheral velocity of the commutator\\nin inches per second. The reciprocal of this time gives the\\nnumber of commutations per second, or what is termed\\nthe frequency of commutation. The frequencies found in\\npractice lie between 200 and 500 per second. While all", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0096.jp2"}, "97": {"fulltext": "OPERATION OF ARMATURES. 85\\nthe current which traverses the coil is suppressed in one-\\nhalf the time taken for commutation, the manner of its\\nvariation is unknown. Parshall and Hobart assume that\\nthe current strength falls sinusoidally. An assumption of\\na uniform decrease with the time yields results quite in\\naccord with practice. The value of the induced voltage\\nthen will be equal to the product of the value of the com-\\nmutated current and the sum of the mutual and self-induc-\\ntance divided by one-half the time occupied in completing\\ncommutation. This value should not exceed 6 volts.\\n55. Prevention of Sparking The limit of the capacity\\nof a machine may be excessive sparking instead of exces-\\nsive heating, and therefore the suppression of sparking by\\nproper design of the machine is of utmost importance.\\nSparking may be prevented\\na. By shifting the brushes till the short-circuited coil\\nis just under the fringe of the pole piece. This counter-\\nacts the effects of self-induction as explained in 5 1. The\\nreversal of the direction of flux in any but the short-cir-\\ncuited coils is to be avoided, since a loss of useful E.M.F.\\nwould then occur.\\nb. By having a stiff field, that is, a field so strong as to\\nsuffer very little skewing because of the armature cross\\nturns. There is then no lag. In practice, air-gap magnetic\\ndensities vary from 2500 to 7500 lines per square centimeter.\\nThe higher densities are to be found in the larger machines.\\nThere is a general tendency to increase the density.\\nc. By nearly saturating the teeth of the armature core.\\nWhen the core teeth are nearly saturated, an increase of\\nload increases the reluctance very markedly, and the demag-\\nnetizing effect of the back turns is restrained on increase", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0097.jp2"}, "98": {"fulltext": "86 DYNAMO ELECTRIC MACHINERY.\\nof load, because of the greater reluctance of the circuit.\\nThis minimizes the shift of the commutating plane from no\\nload to full load, and is a device invariably employed on\\nrailway generators and other machines that have to stand\\nsevere changes of load without change of position of\\nbrushes.\\nd. By using brushes of carbon, brass gauze, etc. In\\nmachines of over ioo volts, carbon brushes are always\\nused. Besides their good wearing qualities, their resistance\\nprevents the flow of a large current in the short-circuited\\ncoil in commutation, and thus a misplacement of the\\nbrushes will not result in so violent a spark. In very low-\\npotential machines, as has already been said, carbon brushes\\nare impracticable, because their resistance causes a too\\ngreat fall of potential. So in these machines copper strip\\nbrushes are employed when possible. When too much\\nsparking occurs with plain copper brushes, a brush of some-\\nwhat greater resistance is employed, such as copper gauze,\\nbrass, brass gauze, etc., according to the requirements of\\nthe case.\\ne. By slotting the pole pieces longitudinally. This in-\\ncreases the reluctance offered to the lines due to armature\\nreactions, and so tends to prevent sparking.\\nf. By properly shaping the pole pieces. The distribu-\\ntion of flux should be such that a coil enters, a weak field\\nfirst, and so gradually comes to the strongest part. If the\\nlines of force are allowed to crowd into the trailing-pole\\ntips, this gradual transition is impossible. If the horns are\\nfarther from the armature surface than the body of the\\npole face, then the air gap and consequently the reluctance\\nat the horns is increased, and the lines are compelled to\\ndistribute themselves more symmetrically. A place suit-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0098.jp2"}, "99": {"fulltext": "OPERATION OF ARMATURES. 87\\nable for commutation is then more readily found. One\\nmay also resort to the shaping of the pole pieces by champ-\\nfering the corners, or by making the pole faces with a cir-\\ncle of greater radius than the armature.\\nThe Sprague Electric Company, in its split-pole type of\\nthe Lundell generator, avoids the distortion of the field\\nunder full load, due to cross magnetizing turns, by making\\nuse of a specially designed pole piece. Fig. 72 repre-\\nsents a cross-section of this generator, and shows the con-\\nstruction of the pole piece. The magnetic flux which\\nenters the pole piece, divides between the two paths a and\\nb. Owing, however, to the greater span covered by the\\nshoe belonging to the part marked b, the magnetic reluc-\\ntance of that part is much- smaller than that of the part\\nmarked a. As a result, the flux does not divide itself\\nequally between the two paths. The part of the pole piece\\nmarked b, under increasing excitation becomes saturated\\nbefore the part marked a. At normal excitation, the flux\\ndensity at b is above 16,000 lines per square centimeter,\\nwhile the flux density in a is but about 10,000 lines per\\nsquare centimeter. In other words, b is pretty well satu-\\nrated, while a has not been brought to a magnetization as\\nhigh as the knee of the magnetization curve. This satura-\\ntion of half of the pole piece is effective in preventing a\\nskewing of the field by the cross turns. This is shown in\\nFigs. 73 and 74, where Fig. 73 represents the development\\nof a 50 kilo- watt Lundell generator, and Fig. 74 shows the\\ndistribution of flux along the line xy of Fig. 73. The\\ndotted line represents the distribution at no load, and the\\nheavy line the distribution at full load. This small dis-\\ntorting effect of the cross turns permits the employment of\\na small air gap without serious sparking.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0099.jp2"}, "100": {"fulltext": "88\\nDYNAMO ELECTRIC MACHINERY.\\nFig. 72.\\niWrt\\n\u00e2\u0096\u00a05SSS\\n^W\\n~%Z2ZZ\\\\\\nfcyfi\\nfflf\\nRfflRRRRflf\\nFig. 73.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0100.jp2"}, "101": {"fulltext": "OPERATION OF ARMATURES. 89\\nRyan compensates for the magnetizing effects of the\\narmature winding by surrounding the armature with a sta-\\ntionary winding, which passes through perforations in the\\npole faces. These stationary windings carry the whole\\ncurrent of the machine. This method prevents all spark-\\ning due to the distortion of the field, but it does not pre-\\nvent the sparking which is due to self-induction and mutual\\ninduction of the armature coils. The latter sparking is\\nprevented to a certain extent by inserting a lug between\\nthe pole horns, which is magnetized by a few series turns.\\nFig. 74.\\n56. Energy Losses in Operation. Besides the energy\\nexpended in exciting the field coils, there are losses of\\nenergy in the armature and connections, as follows\\na. The bearing friction and the windage. This loss is\\ngenerally considered independent of load, but it is ques-\\ntionable whether the friction does not increase somewhat\\nunder loads. This loss is from 1 5 per cent to 40 per cent\\nof the total loss.\\nb. The hysteresis loss in the iron of the core due to the\\ncontinued reversal of the direction of magnetism therein.\\nAccording to Steinmetz s Law, the hysteresis loss in watts,", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0101.jp2"}, "102": {"fulltext": "go DYNAMO ELECTRIC MACHINERY.\\nwhere Fis the volume of iron in cubic centimeters, (B the\\nflux density, n the number of magnetic reversals per sec-\\nond, and rj a constant depending in value upon the char-\\nacter of the iron. A table of values is given on page 29.\\nThe value of varies at different loads and at different\\nplaces, as was shown by Goldsborough, so this loss cannot\\nbe said to be proportional to the speed or any power of\\nthe voltage. The hysteresis loss is from 1 5 per cent to\\n40 per cent of the total losses.\\nc. Eddy currents in the iron and the copper conductors.\\nThese might be expected to vary as the square of the\\nspeed, but they do not for the same reason as in b. Be-\\ncause of the laminated structure of the core, and the\\nslight angular breadth of the conductors, this eddy loss is\\nof small magnitude, from 2 per cent to 10 per cent of the\\nlosses. It may amount to 50 per cent of the losses in\\nthe case of smooth-core armatures. Eddy currents in the\\npole faces, which may be due to any variation in the re-\\nluctance encountered by the lines passing through the\\npoles, are reduced by an increase of air-gap length. They\\nare greatest with armature cores having slots with large\\nopenings at the top, and least with armatures whose in-\\nductors are threaded through inclosed channels in the core.\\nd. The armature resistance loss. This equals I 2 R, where\\nis the total current of the machine, and R the resistance\\nof the armature measured between points rubbed by the\\nbrushes which are drawing the current This is ex-\\nclusive of the transition resistance at the brushes. In\\n500 k. w. machines the PR loss is about 2 per cent of the\\ntotal output. In 5 k. w. machines about 4 per cent, and\\nin smaller machines much greater.\\ne. The friction of the brushes against the commutator.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0102.jp2"}, "103": {"fulltext": "OPERATION OF ARMATURES. 91\\nThis loss varies about as the speed, and its importance is\\ngenerally underestimated. Carbon brushes press upon the\\ncommutator with a force of from 1 to 12 pounds per\\nsquare inch of contact. Railway motors and similar ma-\\nchines have the larger value, while central-station gene-\\nrators have the smaller. The coefficient of friction between\\ncarbon and copper varies from 0.28 to 0.32.\\nf. The resistance of the brushes and the transition re-\\nsistance of the brush contacts. The first loss varies as\\nthe square of the current, and is of considerable magni-\\ntude in low-potential machines. The transition resistance\\nseems to vary inversely as the current, thereby always\\ncausing a constant drop of voltage amounting to from 1\\nto 1.5 volts per transition.\\nThe heat produced by losses b, c, and d, being in the\\narmature itself, must be dissipated by the conduction, con-\\nvection, and radiation. Experience shows that from 2 to\\n2\\\\ watts can be radiated from every square inch of arma-\\nture surface without causing a dangerous rise of tempera-\\nture in the armature core. It is found that about 500\\ncircular mils per ampere in the armature conductors brings\\nthe loss d to such a point that, added to the losses c and\\nb, they -together give about 2 watts per square inch of\\narmature surface hence this value of 500 circular mils per\\nampere is the mean of what is usually adhered to in winding\\narmatures of commercial machines.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0103.jp2"}, "104": {"fulltext": "92 DYNAMO ELECTRIC MACHINERY.\\nCHAPTER VI.\\nEFFICIENCY OF OPERATION.\\n57. Efficiency The following definition and discussion\\nof efficiency is taken from the report of the committee on\\nstandardization of the American Institute of Electrical En-\\ngineers\\nThe efficiency of an apparatus is the ratio of its net\\npower output to its gross power input.\\nElectric power should be measured at the terminals of\\nthe apparatus.\\nMechanical power in machines should be measured at\\nthe pulley, gearing, coupling, etc., thus excluding the loss\\nof power in said pulley, gearing, or coupling, but including\\nthe bearing friction and windage. The magnitude of bear-\\ning friction and windage may be considered as independent\\nof the load. The loss of power in the belt, and the in-\\ncrease of bearing friction due to belt tension, should be\\nexcluded. Where, however, a machine is mounted upon\\nthe shaft of a prime mover, in such a manner that it cannot\\nbe separated therefrom, the frictional losses in bearings\\nand in windage which ought, by definition, to be included in\\ndetermining the efficiency, should be excluded, owing to the\\npractical impossibility of determining them satisfactorily.\\nThe brush friction, however, should be included.\\nWhere a machine has auxiliary apparatus, such as an ex-\\nciter, the power lost in the auxiliary apparatus should not", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0104.jp2"}, "105": {"fulltext": "EFFICIENCY OF OPERATION. 93\\nbe charged to the machine, but to the plant consisting of\\nmachine and auxiliary apparatus taken together. The\\nplant efficiency in such cases should be distinguished from\\nthe machine efficiency.\\nThe efficiency may be determined by measuring all the\\nlosses individually, and adding their sum to the output to\\nderive the input, or subtracting their sum from the input\\nto derive the output. All losses should be measured at, or\\nreduced to, the temperature assumed in continuous opera-\\ntion, or in operation under conditions specified.\\n58. Coefficient of Conversion. This has sometimes\\nbeen called the efficiency of conversion, but because of the\\ndefinition of the last paragraph it is better not to use the\\nword efficiency. The coefficient of conversion is the ratio\\nof the total electrical energy developed in the armature\\nwinding to the total mechanical energy expended.\\nwhere P is the power expended in watts, I t the armature\\ncurrent in amperes, and E t the E.M.F. in volts, developed in\\nthe armature. is always less than unity, because of the\\nfriction and windage of the armature, because of the eddy\\ncurrents in the core and conductors, and because of the\\nhysteresis of the core.\\n59. Economic Coefficient. (rj) This coefficient is equal to\\nthe ratio of the useful electrical energy to the total electri-\\ncal energy developed in the armature circuit. It is always\\nless than unity because of the necessary loss of energy in\\nthe exciting coils and in the armature coils. In the case\\nof a series dynamo, if we let", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0105.jp2"}, "106": {"fulltext": "94 DYNAMO ELECTRIC MACHINERY.\\nE t E.M.F. generated in volts, and\\nE Terminal pressure in volts, then the economic coef-\\nficient for a current of amperes is\\nIE _ E\\nv ~7E t\\nFor shunt dynamos,\\nIE\\n(i+i f )\u00c2\u00a3t\\nWhere /is the current in the outside circuit, l f the current\\nin the field coils, E the pressure at the terminals of the\\nmachine, and E t the total pressure generated.\\nThe efficiency of a machine e is evidently the product of\\nP and rj.\\nFor a series machine, I I t and\\nI t E t E IE\\nFor a shunt machine, I I f I t and\\nI t E t IE IE\\nHence the product of and rj for either machine is the\\nsame, and corresponds to the definition of efficiency.\\n60. Separately Excited Dynamos. At a constant speed\\nand constant exciting current a nearly constant total pres-\\nsure (E f is generated; and it is almost equal to the pressure\\nat the terminals at no load that is, on open circuit. This\\nfollows from the equation for the average pressure,\\nE (\u00c2\u00a733)\\nav 60.10 8 S 33;\\nV\\nwhere is the number of revolutions per second, wS the\\n60\\nnumber of inductors, the flux per pair of poles, and p the", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0106.jp2"}, "107": {"fulltext": "EFFICIENCY OF OPERATION.\\n95\\nnumber of pairs of poles. If the speed be varied, the pres-\\nsure will vary proportionally if no load is on the machine.\\nIf, however, a current be taken off, then the demagnetizing\\neffects of the armature currents become evident in a\\nchange of the value of and there will be a falling off of\\npressure. The amount of this deviation is dependent upon\\nthe composition and saturation of the magnetic circuit.\\n120\\n100\\n80\\n\u00c2\u00abo\\n1-\\no\\n40\\n20\\n30 10\\nAMPERES\\nFig. 75-\\nThis effect is clearly seen in the curve in Fig. 75, where\\nthe armature currents are measured in the X direction, and\\nthe pressure in the Y direction, the conditions of speed and\\nexciting current remaining constant.\\nLet E t the total volts produced,\\nE the volts at the terminals of the machine,\\nR a the resistance of the armature,\\nR the resistance of the external circuit, and\\nthe current under these conditions.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0107.jp2"}, "108": {"fulltext": "96 DYNAMO ELECTRIC MACHINERY.\\nThen for a separately excited machine,\\nE,= f(R+R a\\nE IR, and\\nEI 7 2 R\\nR\\nV EJ r (R E a\\nR+Ra\\nand\\nIn determining the efficiency of a separately excited\\nmachine the energy lost in the exciting coils must be\\ncharged against the coefficient of conversion.\\nThe operation of any dynamo can best be studied by in-\\nspection of a curve which shows the relation existing be-\\ntween the current generated or supplied by the machine,\\nand the voltage under which it operated. Such curves\\nare called Characteristic Curves, and they are generally\\nplotted with currents for abscissae and volts for ordinates.\\nThe characteristic curve for a separately excited dynamo\\nis that shown in Fig. 75.\\n61. Magnetos. A separately excited dynamo whose\\nfield is maintained by a permanent magnet, instead of an\\nelectric magnet, is called a magneto. These machines\\nfrom their similarity, both theoretically and practically,\\nshould be mentioned together. Magnetos are, however,\\ngenerally alternating current machines with slip rings in-\\nstead of commutators. They are used in very great num-\\nbers in telephone subscribers sets, and in many electrical\\nbusinesses for testing out the continuity of concealed con-\\nductors, and in some cases for determining defective\\ninsulation. To the armature is affixed a pinion, meshing\\nwith a gear turned by hand. The alternating current pro-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0108.jp2"}, "109": {"fulltext": "EFFICIENCY OF OPERATION.\\n97\\nduced is passed through the circuit whose continuity it is\\ndesired to determine, and then passes through a polarized\\nbell which is caused to ring\\nThese machines are manufac-\\ntured so as to ring through\\nan external resistance of as\\nhigh as 50,000 ohms without\\nundue effort at the handle.\\nThe cut Fig. 76 shows a com-\\nmercial belt-driven magneto.\\n62. Series Dynamos.\\nLetting E, E v R, R a9 and\\nhave the same significance as\\nbefore, represent by R f the\\nresistance of the field winding, and by R h the resistance\\nof the brushes and transition contacts. Then\\nFig. 76.\\nE IR,\\nE t I(R R f R a R b y\\nwhence it follows\\nEI\\nI 2 R\\nR\\nE t I I*(R R a +R b R f R R a +R h +R f\\nThe value of rj increases as R a R b and R f approach zero.\\nR b is liable to be of greater importance than is imagined.\\nIn low-tension machines all the resistances are small, and\\ncare must be taken that R b does not unduly increase the\\ndenominator of the expression for rj in other words, cop-\\nper brushes should be used on low-voltage machines.\\nThe value of rj varies as R, but the load varies in-\\nversely as R hence rj is a maximum when the load is a", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0109.jp2"}, "110": {"fulltext": "9 8\\nDYNAMO ELECTRIC MACHINERY.\\nminimum, and rj i when R oo, or there is no load.\\nFig. 77 is a curve showing relation between -q and load.\\n63. Characteristic Curve of a Series Machine. Fig.\\n78 shows the curves of a series dynamo. The curve of\\ntotal volts E t is very similar to the magnetization of a\\nmagnetic circuit made\\nup of iron chiefly. It\\nfalls below such a\\ncurve (a) because\\nsaturation causes in-\\ncreased magnetic leak-\\nage, and hence the\\nvalue of in the\\nequation^ 6q iq8\\nis not proportional to\\nthe total flux, and\\n(b) because of the demagnetizing and cross magnetizing\\neffects of the armature currents. The curve E* starts\\nabove zero because of the residual magnetism in the cores\\nof the field magnets. If operated under constant load, a\\nj", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0110.jp2"}, "111": {"fulltext": "EFFICIENCY OF OPERATION. 99\\nseries dynamo will give E, directly proportional to the\\nspeed.\\nThe straight line represents the loss or drop of potential\\ndue to the resistances of the machine, R ay R hy and R f\\nSince drop of potential is proportional to the resistance,\\nthis is a straight line, and must pass through the origin.\\nThis loss line can be established by a point found by as-\\nsuming the lost volts Ei and solving for the current I from\\nthe equation I (R a R 6 R f E z For example, if the\\nresistances R a R*+ R/be assumed as 0.2 ohm, then 10\\nvolts would be lost in them only when 50 amperes were\\nflowing through them. A line drawn through the origin,\\nand a point on the characteristic curve diagram whose\\ncoordinates were 10 volts and 50 amperes, would at every\\npoint give the volts lost in sending the corresponding num-\\nber of amperes.\\nThe curve E showing the E.M.F. at the terminals of\\nthe machine as a function of the current output is found\\nby subtracting the ordinates of the loss line from those of\\nE t and using the differences as the ordinates of E. In\\npractice E t cannot be directly found but the terminal volts\\nand the current can be measured, thus giving the curve E,\\nand from a knowledge of the loss line the curve E t can be\\nderived.\\nThe operation of some special forms of series machines\\nwill be discussed in the chapter on arc-lighting machines.\\n64. Power Lines. Where volts and amperes are used\\nas ordinates and abscissae, lines can be drawn connecting\\npoints of constant product of the two, representing watts\\nor power. Fig. 79 shows such lines drawn for one, two,\\nand three kilowatts. If E be the external characteristic of", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0111.jp2"}, "112": {"fulltext": "IOO\\nDYNAMO ELECTRIC MACHINERY.\\na dynamo, then the curves make it apparent that the ma-\\nchine cannot generate 3 k.w., but that for most values\\nunder 3 k. w.\\nthere will be two\\nloads under which\\nthe generator can\\nrun and yield the\\nsame voltage.\\n65. Shunt Dy-\\nnamos. In\\nshunt-wound ma-\\nchines the cur-\\nrent in the arma-\\nture is the sum of\\nthe current in the\\nfield coils and of\\nthat in the ex-\\nternal circuit, or\\ne\\\\_\\nAMPERES\\nFig. 79.\\nI a I f I- For sake of simplicity we will assume I a\\nPractically this introduces but a small error under ordinary\\nconditions of load.\\nE 2\\nIE I 2 R ~R\\nV\\nIE t I f E I 2 (R R a I 2 R f\\nE 2 E?R a\\n~R ~R r\\nE*\\nE f\\nR\\n1 R a 1 R a R\\nR R 2 R f I ~R R f\\nTo determine what value of R will enable a given ma-\\nchine to operate with a maximum economic coefficient", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0112.jp2"}, "113": {"fulltext": "EFFICIENCY OF OPERATION.\\nIOI\\nplace the differential coefficient of rj y in respect to R con-\\nsidered as a variable, equal to o and solve for R\\ndrj i R n\\ndR R f R 2\\nR= VRJ? f\\nThe external resistance must be a mean proportional be-\\ntween R a and R f and the maximum economic coefficient is\\ni\\nV\\nI +2\\nv/\u00c2\u00a7,\\n66. Characteristic Curve of a Shunt Dynamo. In Fig.\\n80 the curve E is plotted from experimental results obtained\\nwhile the machine is running at various loads. To get satis-\\nfactory results, one should begin with an infinite resistance\\nin the external circuit, which is then reduced step by step.\\nIn some small machines it can be reduced to zero without an\\nextreme elevation of temperature due to excessive currents.\\nAs a rule, only the upper and lower values of E, correspond-\\ning to currents between o and a definite maximum value, can", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0113.jp2"}, "114": {"fulltext": "102 DYNAMO ELECTRIC MACHINERY.\\nbe obtained. The loss line L is obtained by calculation as\\nbefore in the case of the series machine. The curve\\nshowing the relation between external current and total\\nvolts, E u is obtained by adding the ordinates of L to those\\nof E. The drop in E is at first due chiefly to the drop re-\\nsulting from armature resistance. As the current increases,\\nthe effects of armature reaction and saturation of the\\nmagnetic circuit become evident. At the same time E is\\naffected by a decrease of the shunt-field current due to\\nthe fall of potential at the terminals of the field circuit.\\nThis soon becomes the predominating cause of drop, and to\\nsuch an extent that the curve turns back toward the origin.\\nWhen zero resistance is in the external circuit, of course no\\ncurrent flows through the field, and the few volts then\\nproduced are due to residual magnetism. It must be\\nremembered that while E is a double-valued function of\\nit is a single-valued function of R.\\nThe voltage of a shunt machine generally increases more\\nrapidly than the speed. An increase of speed not only in-\\ncreases primarily the number of volts generated, but also\\nincreases the armature flux because of increased excita-\\ntion. The condition of the magnetic circuit as regards\\nsaturation determines whether this secondary influence\\nshall be great or small.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0114.jp2"}, "115": {"fulltext": "CONSTANT POTENTIAL DYNAMOS. 103\\nCHAPTER VIL\\nCONSTANT POTENTIAL DYNAMOS.\\n67. Constant Potential Supply The method of sup-\\nplying, at any point of usage, current at a constant poten-\\ntial irrespective of the load which is there or elsewhere, is\\nused in the distribution of electrical energy for purposes\\nof incandescent electric lighting, for consumption in con-\\nstant pressure motors, and for trolley-car propulsion. The\\ngreat sensitiveness of the candle power of incandescent\\nlamps to a change in voltage, the candle power varying\\nas the fourth power or more of the voltage, requires\\nthat the pressure in lines used for lighting must not vary\\nby more than 3 per cent of its rated value. In street -car\\nwork, where the load suffers tremendous variations, con-\\nstant potential supply is equally as imperative for satisfac-\\ntory operation.\\n68. Methods of Obtaining Constant Potential For\\naccomplishing this result many devices have been tried,\\nthe more important of which are\\na Automatic variation of the resistance in the field cir-\\ncuit of shunt machines.\\nb Automatic change of the position of the brushes and\\ncommutating plgine.\\nc Automatic variation of armature speed.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0115.jp2"}, "116": {"fulltext": "104 DYNAMO ELECTRIC MACHINERY.\\nd Hand regulation of a resistance in series with a shunt\\nfield coil.\\ne Self-regulation.\\nOf these the first three methods are no longer employed,\\nand either hand regulation or self-regulation or both to-\\ngether are relied upon to maintain the constant voltage\\nunder varying loads.\\n69. Hand Regulation Inspection of the characteristic\\ncurves of either the shunt or the separately excited dynamo\\nshows a drop in the voltage as the load increases. This is\\ndue to the internal resistance of the armature and the\\ndemagnetizing effect of armature reaction. In the formula\\nfor the E.M.F. of a machine, E ttJ- the only quan-\\nio 8 6o\\ntity that is practical to vary is This can easily be\\naccomplished by regulating\\nHA ND\\nregulator. the amount 01 resistance m\\nv^sj\\\\M4^x x ?V7V?Wffi7T) a r k eostat w hich is in series\\n(JUUUUUU with the field coils and which\\ntherefore governs the amount\\nin them, as in\\nof current in\\nA^ f Fig. 81.\\nIn distributir\\nFig. 81.\\ndistributing current for\\nuse among a number of con-\\nsumers the current is carried\\nto feeding-points which are\\nnear the locality they supply, but may be distant from the\\nstation. It is desirable to keep the pressure at these\\npoints at a constant value, irrespective of the varying loss\\nof potential that is going on because of the resistance of\\nthe conductors leading to them. To achieve this end the", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0116.jp2"}, "117": {"fulltext": "CONSTANT POTENTIAL DYNAMOS.\\n105\\nEdison system employs feeders to carry the current to the\\nfeeding-points. Each feeder is accompanied by a pilot wire\\nimbedded in the insulation. At the feeding-point the pilot\\nwires are attached to the feeder terminals, and at the sta-\\ntion end are attached to a voltmeter, so that one can, in\\nthe station, regulate the pressure not at the machine ter-\\nminals but at the distant distributing point.\\n70. Field Rheostats. For varying the current in the\\nshunt fields of dynamos, it is usual to employ field rheostats\\nFig. 82.\\nwhich are mounted on the switch-board along with indicat-\\ning instruments. A form of such rheostatic regulators is\\nthe so-called Packed Card Rheostat, manufactured by the\\nGeneral Electric Company. This derives its name from", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0117.jp2"}, "118": {"fulltext": "io6\\nDYNAMO ELECTRIC MACHINERY.\\nthe method of constructing it. A tube of asbestos, in-\\nclosing a steel mandrel, is wound with a chosen amount of\\nGerman-silver wire or ribbon. The tube is then removed\\nfrom the mandrel, and pressed into the form of cards as\\nshown in Fig. 82. These cards are then assembled, with\\ninterposed asbestos, in sufficient numbers to make up the\\nrequired resistance of the rheostat. Iron plates, somewhat\\nFig. 83.\\nwider than the cards, are introduced at intervals, and thus\\nincrease the radiating surface. The whole is held together\\nby iron end plates and bolts, as shown in Fig. 83. Con-\\ntact bolts are connected with various points of the conduc-\\nting part of the rheostat, and these bolts are connected\\nthrough a wiping-finger with the field circuit. Fig. 84 shows\\na rheostat of this type built for regulating a railway gene-\\nrator and arranged to be placed on the back of a switch-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0118.jp2"}, "119": {"fulltext": "CONSTANT POTENTIAL DYNAMOS.\\n107\\nboard with the regulating handle projecting in front.\\nFor the largest generators resistances made of iron grids\\nsupported in iron frames are employed. Both of these\\nconstructions are fire-proof and easily repaired in case of\\naccident.\\nFig. 84.\\nWhen large generators, such as are used in railroad work,\\nhave their field circuits opened, the E.M.F. self-induced\\nby the disappearance of the flux in the fields is liable to\\nreach such a magnitude as to pierce the insulation of the\\nfield coils and destroy their usefulness. To obviate this,\\nbefore the field circuit is broken, the field coils are con-\\nnected (Fig. 85) through a high discharge resistance, and\\nthe current in them is allowed to die out slowly. It is\\nthus unattended with any destructive potential differences.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0119.jp2"}, "120": {"fulltext": "io8\\nDYNAMO ELECTRIC MACHINERY.\\nThe Edison Electric Illuminating Company of New York\\nCity, in the case of its Duane-street generators, allows the\\nfield circuits to discharge themselves through an arc light.\\nAnother form of field rheostat is the Carpenter Enamel\\nRheostat, made by the Ward Leonard Electric Company.\\nIn this rheostat the heat generated is not radiated directly\\nParallel T^esist-ance\\nl^heosbat, Switch\\nPilotTJLampOo=\\nField\\nArmature\\nFig. 85.\\nfrom the surface of the wire, but is conducted to a sup-\\nporting plate, which then becomes the radiating surface.\\nThe resistance wires are surrounded with an enamel, which\\nattaches them to the supporting plates, insulates them\\ntherefrom, and protects them from corrosion. Owing to\\nthe increased radiating surface thus obtained, a shorter and\\nsmaller wire can be used for a given volt-ampere capacity", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0120.jp2"}, "121": {"fulltext": "CONSTANT POTENTIAL DYNAMOS.\\n109\\nthan if the wire were merely exposed to the air. No con-\\nsideration of the mechanical strength of the wire enters\\nFig. 86.\\ninto the design of this resistance, since it is supported and\\nprotected by the enamel. To further increase the radiat-\\nFig. 87.\\ning surface, the back of the plate is provided with raised\\nannular ribs. The~makers claim that this rheostat can radi-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0121.jp2"}, "122": {"fulltext": "no\\nDYNAMO ELECTRIC MACHINERY.\\nate 5 watts for each square inch of one surface. Thus a\\nplate 10 by 10 inches will dissipate 500 watts. The\\nmethod of using iron radiat-\\ning plates for purposes of\\ndissipating large amounts\\nof heat is to be found in\\nthe rheostats of many man-\\nufacturers. Wirt (Fig. 88)\\nincloses resistance wire or\\nribbon in radiating plates,\\ninsulating them from each\\nother by means of mica.\\nOther firms employ sand as\\nan insulating material.\\n7 1 Self -Regulation\\nBy far the most elegant\\nmethod of constant poten-\\ntial regulation is that in\\nwhich the main current of\\nthe machine is utilized in\\nmaintaining constant the magnetic flux through the\\narmature. This is accomplished by passing all or the\\ngreater part of the current produced in the armature a\\nfew times around the field magnets, so that an increased\\nload on the armature increases the magnetizing ampere\\nturns of the field coils. These series turns, when rightly\\nproportioned, can be made to compensate for a part, for\\nall, or for even more than all of the drop. This device\\ncan be used in connection with any other form of\\nexcitation, as permanent magnets, separate excitation,\\nor shunt excitation. In the last case, the dynamo is\\nFig. 88.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0122.jp2"}, "123": {"fulltext": "CONSTANT POTENTIAL DYNAMOS. Ill\\nsaid to be compound wound, as described in 45. If\\nthe machine is designed to maintain a constant pressure\\nat some distant feeding-point, instead of at the machine\\nterminals, the machine is said to be over-compounded, since\\nthe potential at the terminals will rise on increase of load.\\nFrom 3 to 5 per cent over-compounding is frequent in\\nmachines used to supply lighting circuits, and 10 per cent\\nover-compounding is usual in railway generators.\\n72. Economic Coefficient of a Compound Machine.\\nTo discover the value of rj in this case, let R be the resis-\\ntance of the external circuit, R s the resistance of the series\\nturns, R s the resistance of the shunt-field, and R a the\\nresistance of the armature. Then assuming that the cur-\\nrent in the armature is the same as in the external circuit,\\nan assumption which is warranted in the case of commer-\\ncial machines,\\nI 2 R\\nV\\nI 2 R I 2 R a rR s I\\\\ h R sl\\n1\\nR 1\\nR R^ R 2 R 2 T R sh R 1\\nConsidering i?asa variable dependent on rj, and solving\\nfor a maximum of rj\\n-4-^4-^-0\\ndR R s R 2 R 2\\nandt\\nV(* a R s R sl\\nHence it is seen that the maximum economic coefficient is\\nobtained, when the external resistance is the geometric", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0123.jp2"}, "124": {"fulltext": "I 12\\nDYNAMO ELECTRIC MACHINERY.\\nmean between the shunt-field resistance and the sum of\\nthe resistances of the series field and of the armature.\\nUnder these conditions,\\nV\\n\\\\/(R a +R s )R sh\\nI h\\nR\u00e2\u0080\u009e\\nJR.\\n\\\\l(R a +R s )R sh ^/(R a R s )J? s)\\ni +2\\nv/-\\nJ?a -R s\\n-Rsl\\n73. Efficiency of Compound Machines The efficiency\\nof a generator increases with the size, being quite low on\\nsmall machines, and sometimes very high on the larger\\ndynamos. Since the distribution of the magnetic and elec-\\ntrical losses of a generator lies within the discretion of the\\ndesigner, it is possible to so design a machine as to have\\nits point of maximum effi-\\nciency at full load or at a\\nsmaller load, for instance,\\nat one-fourth load. The\\ntwo following cuts show\\nthe relations between effi-\\nciencies and loads on two\\ndifferent machines.\\n100\\n90\\n80\\n70\\n60\\n50\\n40\\n30\\n20\\n10\\ns\\n7\\nr\\nz\\nLU\\n_o\\nU.\\nLl\\nEFFICIENCY CURVE,\\n200 K.W. SIZE 224\\nDIRECT DYNAMO\\nSPEED 150 R P. M.\\nCROCKER-WHEELER ELECTRIC CO-\\n\u00e2\u0096\u00a0\u00e2\u0096\u00a0AMPERE-, N.J.\\no x\\nDin\\n--P,UT\\nKl\\n.O-\\nWA\\nrT\\nA\\n04-\\n74. The Compounding\\nRectifier The gradual\\nsaturation of the fields of\\na generator as full load\\napproaches causes the\\nE.M.F. of even a com-\\npound-wound machine to sag at full load, or if the machine\\nis so heavily compounded that it maintains its potential at\\n40 v 80 ,120 160 .200 24Q.28Q.\\nFig. 89.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0124.jp2"}, "125": {"fulltext": "CONSTANT POTENTIAL DYNAMOS.\\n113\\nfull load, its voltage will rise abnormally at some load less\\nthan full load. To counteract this effect, the Crocker\\nWheeler Company employs a device which is termed a\\ncompounding rectifier. It consists of a suitable resistance\\nshunted across the ter-\\nminals of the series field 10\\ncoils. The full armature\\ncurrent therefore divides\\nbetween this rectifying\\ncoil and the series coils.\\nAs the load increases,\\nmore current passes\\nthrough each, but the\\ncoils are so designed\\nthat this increase heats\\nthe rectifier and causes\\nits resistance to increase,\\nwhile the resistance of\\nthe series coils remains\\npractically unaltered.\\nThus, as the load increases, a larger proportion of the whole\\ncurrent passes through the series coils, and this compen-\\nsates for the sag in voltage that would otherwise have\\nexisted.\\n70. Theory of Self -Regulation. To determine the\\nnumber of turns of wire necessary to be used in the series\\nregulating coils which are wound on the field magnets of a\\ncompound machine,\\nLet n number of shunt turns.\\nn f number of series turns.\\nB number of back turns.\\nz\\nu.\\nh-\\nUl\\n-0\\ncr\\nEFFICIENCY CURVE\\nOF SIZE 170.\\nCROCKER-WHEELER ELECTRIC CO.,\\nAMPERE, N. J.\\nq 7\\noir\\n-PL\\n\u00e2\u0080\u0094J\\nT\\nNKIL\\n3 WATTS\\n287\\n20 40 60\\n100 120 140 160\\nFig. 90.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0125.jp2"}, "126": {"fulltext": "114 DYNAMO ELECTRIC MACHINERY.\\nX= number of cross turns.\\nJ? a S the resistance of the armature plus that of the\\nseries coil.\\nI sh current in the shunt coils.\\nI current in the armature and also in the series coils,\\nsince they are practically the same.\\nE t total pressure developed.\\nE pressure at terminals.\\nX the coefficient of magnetic leakage.\\n(R the reluctance of magnetic circuit when armature\\nis idle. Then\\n\\\\lxi 2 ^tl\\\\ h\\n(R- reluctance with current 7 m armature.\\nLet flux in the armature under different con-\\nditions of working.\\nWhen no current flows in the armature,\\np I.2C\\nWhen the current flows in the armature,\\n5 _ (nI sh n I-BI)= 1 ^a\\\\nI sh +n I--BI]\\n(RX \\\\XI 2 nl\\\\ h A\\nAh\\nwhere -I T\u00e2\u0080\u0094 hence a represents the ratio of the\\nreluctance at no load to the reluctance with the load\\nThe latter value is the greater because of the skewing\\neffect of the cross turns, a, therefore, is less than i.\\nThe flux in the armature which is due to the shunt coils\\nonly, when a current I flows in the armature circuit, is", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0126.jp2"}, "127": {"fulltext": "CONSTANT POTENTIAL DYNAMOS. 1 15\\nThus under load the amature flux due to the shunt coils is\\ndecreased in the ratio,\\nThe series turns must make up this loss, and also compen-\\nsate for the loss due to the back turns and for the electri-\\ncal losses due to the resistances of the armature and the\\nseries coils.\\nT VS j p A VS#p\\nNow, E t and E\\\\\\nand E E\\\\ IR a+8\\nJ 25 V a K 1- sr\\\\ iR a\\n6U X io 8 X 60 L sh J a+s\\nFor convenience let\\n1.25 VSp\\n(RA X io 8 x 60\\nthen E kanl sh \\\\ka (V\u00e2\u0080\u0094 S) a J\\nThe first term of the right-hand member can be written\\nknl sh k (1 \u00e2\u0080\u0094a) nl 8h in which the expression knl sh repre-\\nsents the total voltage developed by the machine at no\\nload, which is therefore the terminal voltage at that load,\\nor in other words is the voltage for which the machine is\\nto be compounded. The equation for the terminal voltage\\nat the load therefore becomes\\nE knl sh k (1 a) nl sh \\\\ka (n r B) E a S L\\nEvidently, if E is to equal knl sh at any and every load,\\nk (1 a) nl sh \\\\ka (V B) B a S 1= o,\\nwhence\\n1 a nl sh B a+S\\nI ka", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0127.jp2"}, "128": {"fulltext": "Il6 DYNAMO ELECTRIC MACHINERY.\\nI Til\\nRemembering that -7 and also that the percentage\\nof electrical energy loss in the field/ -j 100,\\nri pn B\\nIn this value for 11 the first term gives the number of\\nseries turns required to overcome the skewing due to the\\ncross turns the second term gives the series turns neces-\\nsary to compensate for the armature back turns and the\\nthird term shows the number of series turns to balance the\\nloss due to the resistances of the armature and the series\\ncoils.\\nThe difficulty of applying this formula lies in finding a\\nsuitable value for a. This differs in different machines,\\nhaving according to Jackson a value of from .75 to .85 at\\nfull load. It is of course dependent on the load, and has a\\nvalue of unity for no load.\\n76. Views of the American Institute of Electrical\\nEngineers The following statements concerning the\\nregulation of direct current apparatus are taken from the\\nreport of the Standardization committee of the Insti-\\ntute\\nThe regulation of an apparatus intended for the gene-\\nration of constant potential, constant current, constant\\nspeed, etc., is to be measured by the maximum variation\\nof potential, current, speed, etc., occurring within the\\nrange from full load to no load under such constant con-\\nditions of operation as give the required full-load values,\\nthe condition of full load being considered in all cases as\\nthe normal condition of operation.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0128.jp2"}, "129": {"fulltext": "CONSTANT POTENTIAL DYNAMOS. 117\\nThe regulation of an apparatus intended for the gene-\\nration of a potential, current, speed, etc., varying in a defi-\\nnite manner between full load and no load, is to be\\nmeasured by the maximum variation of potential, current,\\nspeed, etc., from the satisfied condition, under such con-\\nstant conditions of operation as give the required full-load\\nvalues.\\nIf the manner in which the variation in potential, cur-\\nrent, speed, etc., between full load and no load is not speci-\\nfied, it should be assumed to be a simple linear relation\\ni. e., undergoing uniform variation between full load and no\\nload.\\nThe regulation of an apparatus may, therefore, differ\\naccording to its qualification for use. Thus the regulation\\nof a compound-wound generator specified as a constant-\\npotential generator will be different from that it possesses\\nwhen specified as an over-compounded generator.\\nThe regulation is given in percentage of the full-load\\nvalue of potential, current, speed, etc. and the apparatus\\nshould be steadily operated during the test under the same\\nconditions as at full load.\\nThe regulation of generators is to be determined at con-\\nstant speed.\\nThe regulation of a generator unit, consisting of a gen-\\nerator united with a prime mover, should be determined at\\nconstant conditions of the prime mover i. e., constant\\nsteam pressure, head, etc. It would include the inherent\\nspeed variations of the prime mover. For this reason the\\nregulation of a generator unit is to be distinguished from\\nthe regulation of either the prime mover or of the gene-\\nrator contained in it, when taken separately.\\nIn commutating machines as direct current generators", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0129.jp2"}, "130": {"fulltext": "Il8 DYNAMO ELECTRIC MACHINERY.\\nand motors, the regulation is to be determined under the\\nfollowing conditions\\na. At constant excitation in separately excited fields,\\nb. With constant resistance in shunt-field circuits, and\\nc. With constant resistance shunting series fields i.e.,\\nthe field adjustment should remain constant, and should be\\nso chosen as to give the required full-load voltage at full-\\nload current.\\nIn constant potential machines the regulation is the\\nratio of the maximum difference of terminal voltage from\\nthe rated full-load value (occurring within the range from\\nfull-load to open circuit), to the full-load terminal voltage.\\nIn constant current machines the regulation is the ratio\\nof the maximum difference of current from the rated full-\\nload value (occurring within the range from full load to\\nshort circuit), to the full-load current.\\nIn over-compounded machines, the regulation is the\\nratio of the maximum difference in voltage from a straight\\nline connecting the no-load and full-load values of terminal\\nvoltage as function of the current, to the full-load terminal\\nvoltage.\\n77. Direct Driven Light Generators. The tendency of\\nmodern engineering practice is to install lighting gene-\\nrators which are directly connected with the steam engines\\nwhich drive them. Owing to the inherent speed of engines\\nbeing smaller than that of generators, direct connected\\narmatures are designed to run at a lower speed than belt-\\ndriven ones. Economical construction demands that they\\nbe of the multipolar type. They require less floor space\\nper kilowatt than the belt-driven machines and this is a\\nquestion of considerable importance in many installations.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0130.jp2"}, "131": {"fulltext": "CONSTANT POTENTIAL DYNAMOS.\\nII 9\\nThey have a higher efficiency of operation consequent\\nupon the elimination of losses in belting and counter-\\nshafting. They also permit of operation of isolated plants\\nin residences and other places where the noise resulting\\nfrom belt-driven machinery would not be tolerated.\\nIn order that standard generators may be easily con-\\nnected with engines of any make, and vice versa, commit-\\ntees from the American Societies of Electrical Engineers\\nand of Mechanical Engineers have recommended the\\nadoption of the following standard sizes, speeds, and arma-\\nture shaft fits\\nSizes in K. W. Capacity\\nSpeeds in Rev. per Minute\\nArmature Fit in Inches\\n5\\n450\\n3\\n7-5\\n425\\n3\\n10\\n400\\n3 l A\\n15\\n375\\n3 l A\\n20\\n35\u00c2\u00b0\\n4\\n25\\n3 2 5\\n4\\n35\\n310\\n4%\\nSizes in K. W. Capacity\\nSpeeds in Rev. per Min.\\nArmature Fit in Inches\\n50\\n290\\n5\\n75\\n275\\n6\\n100\\n250\\n7\\n125\\n2 35\\n7y 2\\n150\\n220\\n8\\n200\\n200\\n9\\n250\\n190\\n10\\n300\\n180\\nn\\nFig. 91 shows a machine made by the Westinghouse\\nElectric Manufacturing Company in standard sizes of 100,\\n150, 200, 500, and 675 k. w., at 125 volts. The field\\nframe is circular and divided in a vertical plane. The pole\\npieces are of laminated sheet steel, cast into the frame.\\nProjecting from the field frame are brackets, which hold\\nand carry the brush-holder mechanism. This consists of\\na ring concentric with the axis of the armature. Upon\\nits rim is a gear, which engages with a worm operated by\\na hand-wheel. The simultaneous shifting of the brush\\ncan be accomplished by the turning of the hand-wheel.\\nThe slotted armature disks are made of sheet steel, and", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0131.jp2"}, "132": {"fulltext": "120\\nDYNAMO ELECTRIC. MACHINERY.\\nare held together by cast-iron end plates. The disks and\\nend plates are mounted upon a cast-iron spider, which also\\ncarries the commutator. The spider is fitted so as to be\\npressed upon the engine shaft and keyed to it. The con-\\nFig. 91.\\nductors are bars of copper, which are forged into shape on\\ncast-iron formers wound and insulated with mica and ful-\\nlerboard.\\nFigs. 92 and 93 represent a front and rear view of a", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0132.jp2"}, "133": {"fulltext": "CONSTANT POTENTIAL DYNAMOS.\\n121\\nGeneral Electric Company s Form L generator. The\\nframe, of a circular form, is divided in a horizontal plane,\\nand is made of soft cast iron. To it are bolted pole pieces\\nFig. 92.\\nwhich are made of soft cast steel. A skeleton, circular,\\ndisk-like brush-holder yoke is fastened to the frame by\\nmeans of three slots and bolts, and is capable of sufficient\\nangular rotation to permit of the proper adjustment of", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0133.jp2"}, "134": {"fulltext": "122\\nDYNAMO ELECTRIC MACHINERY.\\nthe brushes. The movement is accomplished by means of\\na hand-wheel and pinion. The armature spider is so con-\\nstructed that it receives the commutator as well as the\\nFig. 93.\\ndisks and the armature windings. It is open so as to offer\\nno obstruction to the free and thorough circulation of air\\nthrough it, which permits of a perfect ventilation. The\\nwindings are of copper bars, and the end connections are", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0134.jp2"}, "135": {"fulltext": "CONSTANT POTENTIAL DYNAMOS.\\n123\\nsupported by flanges which protect them from mechanical\\ninjury. The commutator shell is pressed upon the arma-\\nture spider.\\nFig. 94.\\nThe Crocker Wheeler Electric Company s direct-con-\\nnected and belt-driven generators differ from others which\\nhave been described, chiefly because of the shape of the\\nfield-magnet frame and the method of armature winding.\\nThe field frame shown in Fig. 94 is circular in form, and is", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0135.jp2"}, "136": {"fulltext": "124 DYNAMO ELECTRIC MACHINERY.\\ndivided in a horizontal plane. These frames are of cast\\niron, and have short internal flanges on each side, which\\nmechanically strengthen the frame, and offer considerable\\nprotection from mechanical injury to the field coils. The\\nround poles are of cast steel, cast-welded into the frame.\\nThey are provided with removable cast-iron shoes, which\\nare clamped in place after the field coils have been put on.\\nThe armatures, instead of being bar-wound, are wound\\nVig- 95.\\nwith solid copper wire of large sizes, which are triple\\ncotton covered. The conductors are threaded through\\ntubes which are placed one upon the other, and which are\\nmade of micanite cloth and press-board rolled up on a\\nform and glued together. The brush holders and brush\\nrigging were shown in Figs. 48 and 49.\\nThe Sprague Electric Company manufactures two types\\nof Lundell generators, both for direct connection and for\\nbelt connection. They are, namely, the split-pole type,\\nwhich employs the principle laid down in paragraph 55", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0136.jp2"}, "137": {"fulltext": "CONSTANT POTENTIAL DYNAMOS.\\n125\\nfor compensating for armature reaction, and the single-coil\\ntype, which takes its name from the peculiar shape of the\\nfield frame and poles, which permits of the use of but a\\nsingle field coil. Both frames are of the circular type,\\nFig. 96.\\nthe split-pole field being divided in a horizontal plane,\\nand the single-coil type being divided in a vertical plane\\nwhich is perpendicular to the axis of the armature. A\\nsplit pole, with its windings, is shown in Fig. 95. The\\ncompound coil is placed nearer the shoe than the shunt", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0137.jp2"}, "138": {"fulltext": "126\\nDYNAMO ELECTRIC MACHINERY.\\ncoil, and both are kept in place by lugs, as shown in the\\nfigure. Fig. 96 shows a 6-pole, single-coil type field-\\nmagnet frame with its coil inclosed in the frame. The\\nbrush holders which are employed on both types of ma-\\nchine are illustrated in Fig. 97, the brushes being of", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0138.jp2"}, "139": {"fulltext": "CONSTANT POTENTIAL DYNAMOS.\\n127\\ncarbon used radially, and being perforated to receive a bolt\\nfor clamping them to the holders.\\nThe Bullock Electric Manufacturing Company s direct\\nconnected generator, Fig. 98, has an external appearance\\nsimilar to that of the generators of other companies. It\\nFig. 98.\\nis different from them, however, in having peculiarly con-\\nstructed poles. These poles are made up of laminated\\nsteel stampings, which are much thinner than are ordi-\\nnarily used, and which have the peculiar shape shown in\\nFig. 99. In assembling these stampings to form the pole,\\nevery alternate one is reversed from the position which is", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0139.jp2"}, "140": {"fulltext": "128\\nDYNAMO ELECTRIC MACHINERY.\\nindicated in the figure. The method of assembling is\\nshown in Fig. ioo. After assembling, it will be seen that\\nthe face of the pole for a short depth contains but one-half\\nas much iron as the main body of the pole. This results,\\nunder normal excitation, in a saturated pole face. It has\\nthe same effect in preventing distortion of the field under\\nthe influence of armature reaction, as saturation of the\\nteeth of the armature core. The teeth can, therefore, be\\nFig. 99.\\nFig. ioo.\\noperated at a smaller magnetic flux density. The hystere-\\nsis losses in the teeth can accordingly be made smaller.\\nThe thinness of the stampings, and the ideally perfect\\nlamination of the pole face, permit the use of a smaller\\nratio of tooth width to slot width, without the excessive\\neddy current loss in the pole face which would occur in\\nordinary machines. The possibility of using narrow teeth\\nresults in a reduction of the inductances of the armature\\ncoils. This facilitates effective commutation.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0140.jp2"}, "141": {"fulltext": "CONSTANT CURRENT DYNAMOS. 129\\nCHAPTER VIII.\\nCONSTANT CURRENT DYNAMOS.\\n78. Direct Current Arc Lighting Generators. For\\nlighting by arc lights where considerable energy is ex-\\npended at the points of illumination, and where these\\npoints are separated from each other by considerable dis-\\ntances, it is sometimes economical and desirable to connect\\nthe lamps in series and use a constant current. A single\\nline then completes a circuit of all the lamps (Fig. 101).\\nThe line can be made\\nof much smaller wire\\nthan in the case of a\\nconstant pressure cir-\\ncuit, for on a constant\\ncurrent circuit as the\\nload increases the power\\nor energy transmitted is FigT^oi.\\nincreased by raising the\\npotential, the current remaining unaltered while in a con-\\nstant pressure circuit an increase of load is met by an\\nincrease of current, and the wires of the line have to be of\\nsufficient size to safely carry the maximum. The size of\\nwire necessary is dictated, not by the energy transmitted,\\nbut by the current flowing, hence a wire large enough to\\nsupply just one lamp of a constant pressure circuit can\\nsupply all the lamps of a constant current circuit.\\nO", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0141.jp2"}, "142": {"fulltext": "130 DYNAMO ELECTRIC MACHINERY.\\nThe more general forms of arc lamps have what is\\ntermed a spherical candle-power of 800, 1200, or 2000.\\nLamps used in search-lights and in light-houses often ex-\\nceed this in candle-power, and may consume many more\\namperes. The arc lamp of 800 candle-power takes a cur-\\nrent of 4.5 amperes, that of 1200 candle-power 6.6 to\\n6.8 amperes, and that of 2000 candle-power 9.6 to 9.8\\namperes.\\nAn ordinary arc lamp, as it is trimmed and adjusted for\\ngeneral use, requires between 45 and 50 volts to force its\\nrated current through it. A generator supplying a circuit\\nof say 2000 candle-power lamps with n such lamps in the\\ncircuit must be capable of generating a constant current of\\n9.8 amperes. It must be able to regulate its pressure\\nbetween the limits of 50 and 50/2 volts. This is necessary\\nin order that it may operate all the lamps or any part of\\nthe whole number.\\nThe current of an arc-light machine must not exceed\\nnor fall below its normal value, no matter how suddenly\\nthe load is varied for the slightest change, even for a very\\nbrief instant of time, affects the quality of the light at the\\nlamps. It is obvious that some mechanical device could be\\napplied to an ordinary shunt -wound generator to cause it\\nto give constant current, either by changing the position of\\nthe brushes or by varying the ampere turns of the field\\ncoils. However, any such device would be slow of opera-\\ntion, and a sudden short circuit would cause a destructive\\ncurrent to flow before the regulator completed its action.\\nIt is, therefore, necessary to rely on the armature reactions\\nfor regulation, since they vary simultaneously with the cur-\\nrent. All successful constant current machines are con-\\nstructed on this principle. The machine is designed with", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0142.jp2"}, "143": {"fulltext": "CONSTANT CURRENT DYNAMOS. 131\\na field of very great magnetizing power, the armature re-\\nactions are very great, and thus the total flux effective in\\nproducing E.M.F. is reduced. A slight increase of current\\nin the armature materially increases the armature reactions.\\nThe effective flux is thus reduced, and the pressure falls\\nuntil the current returns to its normal value. Thus the\\nmachine is completely and instantly self-regulating. Since\\nthe field magnetization is kept constant and the machine\\nproduces constant current the field coils are series wound\\non all arc-light generators, and the cores of the field\\nmagnets are worked at a very high magnetic density, since\\nthe magnets are then more insensible to slight changes in\\nthe magnetizing force. In commercial machines the den-\\nsities in the field cores are from 17,000 to 18,000 lines per\\nsquare centimeter for wrought iron or steel, and from 9000\\nto 11,000 lines for cast iron.\\nIn the armature high magnetic density is also required\\nto prevent a sudden rise of voltage when the circuit is\\nbroken. With no current in the armature, the total mag-\\nneto-motive force of the field magnets would be effective\\nin producing E.M.F. and a destructive rise of pressure\\nwould result, since the total M.M.F. of the field magnets\\nis much greater than the normal effective M.M.F. But a\\nhigh magnetic density in the armature core leaves the latter\\nincapable of receiving such an increase of flux, and there-\\nfore destructive voltages are avoided. In practice the arma-\\nture core is designed to have a density of from 15,000 to\\n20,000 lines per square centimeter at its minimum cross-\\nsection.\\nA consideration of the foregoing theory of regulation\\nshows that the following conditions should obtain more or\\nless completely in a successful constant current generator", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0143.jp2"}, "144": {"fulltext": "132 DYNAMO ELECTRIC MACHINERY.\\n(a) since the current is small, there must be a great num-\\nber of armature turns (b) the magnetic field of the ma-\\nchine must be much distorted (c) the path of the lines of\\nforce of the field coils must be long and of small area, so\\nthe M.M.F. cannot be readily changed (d) the path of the\\nlines of force due to armature magnetization must be short\\nand of great area, so the M.M.F. of the armature will change\\nwith the slightest change of current and (e) the pole piece\\nmust be worked at a high density.\\nEvidently extreme difficulty is found in so designing the\\ndifferent parts of the machine as to give proper considera-\\ntion to each of the conditions and yet produce a machine\\nthat will regulate for constant current at all loads. This\\nleads to the introduction of automatic mechanical devices\\nfor aiding in the regulation. These devices must not be\\nconsidered as being the sole regulators, for in every case\\nthey are secondary to the natural self -regulating tendency\\nof the armature. In general they regulate for the gradual\\nand greater changes of load, while the armature reactions\\ntake care of the smaller and more sudden fluctuations.\\nThere are two general systems of regulating arc dynamos.\\nThe first method is to cause the machine to develop an\\nE.M.F. in excess of that required for the load, and to then\\ncollect an E.M.F. just sufficient for the load in hand. This\\nis done by shifting the brushes from the neutral plane (\u00c2\u00a750).\\nIn a closed-coil armature this causes a counter pressure to\\nbe developed in those conductors lying between the neutral\\nand the commutating planes. This reduces the pressure\\nto the desired amount. In an open-coil armature the\\nbrushes, when in the maximum position, connect to the\\ncircuit those coils of the armature which at that instant\\nhave the maximum E.M.F. generated in them. By shift-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0144.jp2"}, "145": {"fulltext": "CONSTANT CURRENT DYNAMOS. 133\\ning the brushes either way coils can be connected to\\nthe circuit which have some E.M.F. less than the total\\nE.M.F. generated in them, and the amount of shifting\\nregulates the pressure on the line.\\nThe second method of arc-light dynamo regulation is to\\nvary the magnetizing force in the field magnets just enough\\nto put the required pressure on the line. Since the mag-\\nnetizing force is dependent on the ampere turns of the field\\ncoils, it can be varied either by cutting out or short circuit-\\ning some of the turns or by changing the current in them\\nby means of a variable resistance which is shunted across\\nthe field terminals. In practice both these methods have\\nbeen used.\\nWhether regulation is effected by changing the position\\nof the brushes, or by changing the field excitation, sparking\\nwill occur at the points of collection of the current if means\\nare not provided to avoid it. Non-sparking collection could\\nbe obtained if the field were perfectly uniform all around\\nthe armature. In general this condition is impracticable,\\nsince it requires almost the whole armature to be covered\\nby the pole faces, and it requires the density in the gap\\nbeneath them to be uniform. Considerations of magnetic\\nleakage and armature reaction render almost impossible the\\nsatisfying of these conditions. Another and more prac-\\ntical method is to employ for collection at one terminal of\\nthe machine two brushes connected in parallel. These are\\nmoved in opposite directions, thus giving the effect of a\\nsingle brush of varying circumferential contact, whose\\ncenter can always be kept in the neutral plane. This\\nprevents bad sparking. The device is used quite success-\\nfully in practice. There is, however, some question as to\\nthe advisability of resorting to it.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0145.jp2"}, "146": {"fulltext": "134\\nDYNAMO ELECTRIC MACHINERY.\\n9. The Brush Machine. Fig. 102 shows a standard\\n160-light Brush arc generator, made by the General\\nElectric Company. The armature revolves between the\\n14444444.\\n1/4444441\\nFig. 102.\\nopposed pole faces of two sets of field magnets. Like\\npoles are opposed to each other. The flux, therefore,\\ntakes a path out of the opposing pole faces into the arma-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0146.jp2"}, "147": {"fulltext": "CONSTANT CURRENT DYNAMOS.\\n135\\nture core, and then circumferentially through the core and\\nout into the next pair of opposing pole faces.\\nFig. 103.\\nThe armature, Fig. 103, consists of a number of coils or\\nbobbins placed on a ring core of greater radial depth than\\nbreadth, and the pole faces cover the sides instead of the\\nFig. 104.\\ncircumference. The bobbins are protected by an insulat-\\ning box, shown in Figs. 104 and 105, but are not surrounded\\nby any masses of metal. This fact, coupled with the fact\\nthat the armature is of such a shape as to cause great air", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0147.jp2"}, "148": {"fulltext": "136\\nDYNAMO ELECTRIC MACHINERY.\\ndisturbance, insures exceptional ventilation of the armature,\\nand tends to prevent the roasting out of the coils when\\nsubject to an overload. This machine is of relatively slow\\nspeed, the larger sizes running at only 500 R.P.M.\\nFig. 105.\\nAt a given instant of time, the different coils on the\\nmoving armature have E.M.F s of widely different magni-\\nFig. 106.\\ntudes induced in them. The commutator, Fig. 106, is so\\ndesigned that it connects the coils of highest E.M.F in\\nseries with each other to the external circuit, and con-\\nnects the coils of medium E.M.F, in multiple with each", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0148.jp2"}, "149": {"fulltext": "CONSTANT CURRENT DYNAMOS.\\n137\\nother to the external circuit, while those of smallest E.M.F.\\nare cut out entirely from the circuit.\\nThe bearings are self-lubricated by means of rings.\\nSince the poles are on the sides of the armature, side\\nFig. 107.\\nplay in the bearings must be prevented. To this end the\\ncommutator end of the shaft is turned with six thrust col-\\nlars, as seen in Fig. 107, which are engaged by correspond-\\ning annular recesses in the brasses.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0149.jp2"}, "150": {"fulltext": "138\\nDYNAMO ELECTRIC MACHINERY.\\nRegulation on these machines is effected by a variable\\nresistance in shunt with the field coils; and as the field\\ncurrent is changed the position of the brushes is also\\nchanged, not to collect current at a lower voltage as de-\\nscribed in 78, but to obtain sparkless collection. These\\ntwo operations are performed by a regulator (Fig. 108),\\nFig. 108.\\nwhich is attached directly to the frame of the machine.\\nThe mechanism consists of a rotary oil-pump driven by a\\nbelt from the armature shaft, a balance valve of the piston\\ntype, and a rotary piston in a short cylinder, which is\\ndirectly connected to an arm sweeping the contacts of the\\nfield-shunt rheostat. The valve is operated by a lever", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0150.jp2"}, "151": {"fulltext": "CONSTANT CURRENT DYNAMOS.\\n139\\nactuated by a controlling electro-magnet which is energized\\nby the whole generator current. At normal current the\\nvalve is centrally placed, and the oil from the pump flows\\naround the overlapping ports into the reservoir without\\neffect (See Fig. 109). If the current rises above the nor-\\nmal, the armature of the controlling magnet is attracted,\\nthe balance valve moves up, and oil enters the cylinder,\\nFig. 109.\\nmoving the rotary piston in a clockwise direction. The\\nshaft of this piston moves the arm of the rheostat, cutting\\nout resistance and thus lowering the field exciting current.\\nAt the same time a pinion on the shaft, seen in Fig. no,\\nactuates a rocker arm which moves the brush holders to a\\nposition such that the collection by the brushes will be\\nsparkless. When the current returns to normal the\\nadjusting spring, seen in Fig. in, returns the lever and\\nbalance valve to the central position. If the current falls", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0151.jp2"}, "152": {"fulltext": "140\\nDYNAMO ELECTRIC. MACHINERY.\\nFig a no.\\nFig. in.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0152.jp2"}, "153": {"fulltext": "CONSTANT CURRENT DYNAMOS. 141\\nbelow the normal, these operations are reversed. The\\ntension of the adjusting spring can be regulated from the\\noutside of the dust-proof case by a hard rubber knob.\\nFrom the nature of the case the parts are always well\\nlubricated.\\nIt is claimed for this regulator that it can bring the cur-\\nrent back to normal from a dead short-circuit in from 3^ to\\n4 seconds.\\n80. The Westinghouse Arc-Light Machine Fig. 112\\nshows a 7 5 -light direct current arc-lighting generator,\\n\u00e2\u0080\u00a2made by the Westinghouse Electric and Manufacturing\\nCompany. It is of rigid construction, the bearing sup-\\nports being cast integral with the frame. For facilitating\\ntransportation and repairs the yoke parts in the middle\\non a horizontal plane. The bearings are of the self-\\noiling, self-aligning type described in 41. The armature\\nshown in Fig. 1 1 3 is of the open-coil type, which gives a\\nunidirectional but not absolutely continuous current. The\\nslight pulsations of the current thus set up, while not\\naffecting the steady mean value of the current, cause a\\nslight constant vibration in the mechanism of the lamps\\nthat helps overcome any tendency to stick or a failure to\\nfeed the carbons. A unique feature of this armature con-\\nsists in its having two separate sets of windings on the\\nsame core, each set having its own commutator. The coils\\nand commutators are so arranged that while a set of coils\\nof one winding is being cut into or out of the curcuit a set\\nof the other winding is supplying current to the line. It is\\nclaimed for this method of connecting open-coil armatures,\\nthat it yields a more satisfactory current, and obviates the\\nvicious sparking at the commutator found in other types", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0153.jp2"}, "154": {"fulltext": "142\\nDYNAMO ELECTRIC MACHINERY.\\nof open-coil machines. The armature is made of lami-\\nnated steel sheets punched with T-shaped teeth between\\nthe winding slots. The armature coils are wound on\\nFig. 112.\\nmolds, and insulated and mounted on the armature as\\nshown in Fig. 114. They are held in place by wooden\\nwedges forced into the loops left at the ends of the arma-\\nture. This construction admits of removing one coil for\\nrepairs without disturbing any of the other coils.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0154.jp2"}, "155": {"fulltext": "CONSTANT CURRENT DYNAMOS.\\n143\\nThis machine differs from\\nthe general type of arc-light-\\ning machines in that it is\\nseparately excited, a small\\nauxiliary machine generating\\ncurrent for the field coils at\\n100 volts. This obviates the\\npossibility of danger from a\\ntoo high pressure resulting\\nfrom an open circuit.\\nRegulation is obtained by\\ncareful design, so that the\\narmature reactions cause the\\nvoltage to vary in just the\\nproper proportions, as de-\\nscribed in 78. The exciting\\nfield current is regulated to\\ngive the proper excitation by\\na series rheostat. By this\\nmeans the line current can\\nbe raised or lowered slightly\\nif desired, without affecting\\nthe self -regulation.\\nFig. 1 1 5 shows the double\\ncommutator of this machine.\\nThe segments are easily re-\\nmoved and replaced in case\\nthey wear or burn out.\\n81. The Wood Arc Dynamo. Fig. 116 shows a Wood\\nconstant current dynamo for lighting 125 2000 c.p. lamps.\\nThis machine claims an efficiency of 90 per cent on full", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0155.jp2"}, "156": {"fulltext": "144\\nDYNAMO ELECTRIC MACHINERY.\\nload. The bearings are self -oiling, and may be removed\\nfor repairs or inspection without removing the armature.\\nThe armature has large radiating surface and shallow wind-\\nFig. 114.\\ning, and its temperature does not rise more than 40 C.\\nabove the temperature of the room. This armature is of\\nthe closed-coil type, requiring a commutator of many seg-\\nments with but a small potential between any two adjacent", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0156.jp2"}, "157": {"fulltext": "CONSTANT CURRENT DYNAMOS.\\n145\\nones. This fact, and the use of two brushes in parallel, as\\nexplained in 78, obviates all sparking.\\nThis machine operates by generating full pressure at all\\ntimes, and by automatically setting the brushes to take off\\njust such potential as is necessary. This allows of regu-\\nlation without making use of rheostats, separate ex-\\nciters, wall controllers, motors, or relays. The regulating\\nFig. 115.\\nmechanism is set in operation by a sensitive and rather\\npowerful electro-magnet excited. by the main armature\\ncurrent. This attracts a lever which is restrained by an\\nadjustable coiled spring. A variation in the current\\nstrength causes this lever to throw into train one or the\\nother of two oppositely revolving fiber friction cones, which,\\nacting through gears and levers, shifts the brushes the re-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0157.jp2"}, "158": {"fulltext": "146\\nDYNAMO ELECTRIC MACHINERY.\\nquisite amount, and also varies their angular contact or\\ncollecting extent. All the delicate parts of this mechanism\\nare inclosed in the pillar supporting the commutator end\\nof the armature shaft, and are thereby protected from\\nFig. 116.\\ninjury, dust, and grit. The wearing surfaces of this regu-\\nlator are all large and the speed is slow, so that wear is re-\\nduced to a minimum. Without any change of adjustments\\nthis regulator will operate when run either way, which is\\nan advantage when two or more dynamos are run from one\\nengine, and economy of space is essential, or in case of\\naccident to a prime mover.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0158.jp2"}, "159": {"fulltext": "CONSTANT CURRENT DYNAMOS.\\n147\\n82. The Excelsior Arc Dynamo. This machine, Fig.\\n117, is a closed-coil ring armature generator, having pole\\nfaces that cover both the sides and the circumference of\\nthe armature. The interesting feature of this machine is\\nthe method of regulation. The proper potential is sup-\\nplied to the line by using both methods of control in con-\\njunction that is, sections of the field windings are cut in\\nor out of circuit, and at\\nthe same time the posi-\\ntion of the brushes is\\nshifted. The proper\\nmotion of the field regu-\\nlator arm and of the\\nbrush holder is obtained\\nby means of a small\\nmotor whose field is\\nsneaked from the\\nmain magnets of the\\nmachine. This motor\\nis operated by a device\\nshown in Fig. 118. The\\nwhole device is inserted\\nin series with one of the\\nmains from the gener-\\nator. The right-hand\\nlever is of insulating material, with the contact blocks\\na and b properly placed upon it. The left-hand lever\\nis of conducting material, and is capable of being attracted\\nby the electro-magnet which is excited by the main\\ncurrent. The magnet and spring are so adjusted that\\nwhen the normal current is flowing, both a and b are\\nin contact with the left lever, and the current flows in the", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0159.jp2"}, "160": {"fulltext": "148\\nDYNAMO ELECTRIC MACHINERY.\\nthree shunt paths, R, R ly and R 2 There will be no cur-\\nrent in the armature of the regulating motor, since the\\npotential at brush x is equal to the potential at brush y.\\nIf now the line current becomes too strong the magnet\\nattracts the left lever to it and the contact at a is broken.\\nFrom Dynamo\\nFig. Il8.\\nImmediately the current flowing through b divides at the\\nbrush x, part going through R 2 and part through the motor\\narmature and R v The motor will then revolve in a given\\ndirection, and by simple mechanical devices will cut out\\nsections of the field windings, and will shift the brushes\\nuntil the normal current is flowing, when contact is again", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0160.jp2"}, "161": {"fulltext": "CONSTANT CURRENT DYNAMOS. 149\\nmade at a and the controlling motor stops. If the line\\ncurrent drops below normal, the spring pulls the lever\\naway from the magnet and the contact at b is broken.\\nPart of the current then flows from y to x through the\\nmotor armature. It therefore revolves in a direction op-\\nposite to that which it had before. The brushes on the\\ndynamo are shifted back again, and more sections of field\\nwinding are put into circuit.\\nIn practice the levers and the magnet are mounted on\\nthe wall or the switch-board, while the regulating motor is\\nmounted on the dynamo frame.\\nWhen the current is broken at a or b, there is no serious\\nsparking, since there are always two circuits in shunt with\\nthe break. The whole current of the dynamo does not\\nexceed ten amperes and the resistances R, R v and R 2 are\\nso proportioned that only a small portion of that flows\\nthrough a or b.\\n83. The Ball Arc Generator. Fig. 119 shows a double\\narmature, automatic regulating constant current generator,\\nmade by the Ball Electric Company. Two independent\\ncircuits, each automatically controlled, can be operated\\nfrom the one machine, since it has two distinct armatures,\\ncommutators, and regulators. The advantage claimed for\\nthis arrangement is that the pressure has to be but half as\\nhigh as if the two circuits were united and fed by a single\\narmature. Yet if it be undesirable to bring the ends of\\ntwo circuits into the power-house, they can be connected\\nin series, and fed by the two armatures also connected in\\nseries, and then the voltage per armature will be half that\\nof a single armature machine giving like results.\\nThe armatures are of the closed-coil ring type. The air", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0161.jp2"}, "162": {"fulltext": "ISO\\nDYNAMO ELECTRIC MACHINERY.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0162.jp2"}, "163": {"fulltext": "CONSTANT CURRENT DYNAMOS. 151\\ngap between pole faces and armature is short in length and\\ngreat in area, requiring a minimum of magnetic excitation.\\nThe commutator is built up of a great number of segments,\\nthe potential between any two adjacent segments not ex-\\nceeding fifteen volts. This assures sparkless commutation.\\nThis generator is regulated by shifting the brushes until\\npressure of a suitable magnitude is collected.\\nA magnetic body placed in a magnetic field will tend to\\nrotate until the longest axis is parallel to the magnetic lines\\nof force. This principle is applied to the Ball regulator as\\nfollows A magnetic portion of the brush carrier is made a\\npart of the magnetic circuit, and is placed in a recess of the\\ndynamo frame. It tends to assume an axial position with\\na force varying as the flux through it. As the line current\\nincreases the flux increases, and the brush holder, which is\\nmounted on ball bearings, rotates, shifting the brushes the\\nrequired amount. The impulse to regulate is applied\\ndirectly to the brush holder, instead of being communi-\\ncated to it by by a more or less complex mechanism. The\\nmagnetic tendency to shift the brush holder is opposed by\\ngravity.\\n84. The Thomson-Houston Dynamo. The Thomson-\\nHouston arc generator is of a type entirely different from\\nthe other machines here described, not only in appearance,\\nbut also in method of armature winding and of regulation.\\nA view of this machine is given in Fig. 1 20. Each field\\ncoil has for its core an iron tube, flanged exteriorly at each\\nend to form a recess for the windings, and fitted at the\\narmature end with a concave iron piece that surrounds part\\nof the armature. This tube, with the flanges and the cup-\\nshaped end,, is cast in one piece. The farthermost flange", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0163.jp2"}, "164": {"fulltext": "152 DYNAMO ELECTRIC MACHINERY.\\nof each field core is bolted to a number of wrought-iron\\nconnecting-rods which hold the magnets in place, protect\\nthe field windings, and take the place of the yoke of other\\nmachines in completing the magnetic circuit. The mag-\\nnets are mounted on a frame, including legs and bearing\\nsupports for the armature shaft.\\nThe armatures of the older machines of this type are\\nspheroidal in shape, while the more recent ones have ring\\narmatures which are more readily repaired or rewound.\\nThe winding of either form of armature is peculiar in that\\nonly three coils are employed, set with an angular dis-\\nplacement from one another of 120 degrees. In the ring\\narmature no difficulty is found in properly winding these\\ncoils but in the old spherical armature the following de-\\nvice was employed to secure the windings, and give each\\nof them the same average distance from the pole face. A\\nhollow spheroidal iron core was keyed on the shaft. The\\ncore had three rows of externally projecting wooden pins.\\nBetween these pins the coils were wound, half of coil A\\nbeing wound first, then at 120 degrees distance half of coil\\nB was wound, covering parts of coil A. Then at 120 de-\\ngrees from both A and B all of coil C was wound. Over\\nthis, but in its proper angular position, the other half of\\ncoil B was wound, and finally the rest of coil A was put in\\nplace. By this arrangement the average distance of each\\ncoil from the pole face or from the iron core was the same.\\nIn either type of armature the inner ends of the three coils\\nare joined to each other, and are not attached to any other\\nconductor, an arrangement unique in direct current dyna-\\nmos. The outside ends are connected to the segments of\\na three-bar commutator, from which the current is collected\\nby four copper brushes connected in multiple.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0164.jp2"}, "165": {"fulltext": "CONSTANT CURRENT DYNAMOS.\\n153\\nRegulation is obtained by shifting the brushes in the\\nfollowing manner. Fig. 1 2 1 shows the two possible rela-\\n1\\n1\\n%m..\\nj\\\\ 11\\n^^T-Y\\n1 itmPmm\\n^A -^t\\niBj Bf \u00c2\u00a3fR|\\nk 1 imsi!\\nSPS^^^^\\nt- ^S?^--; A \u00e2\u0096\u00a0J\u00c2\u00a3 v-.\\ni\\n.:.j; r 5\\n\\\\.;\u00c2\u00abr .2\u00c2\u00a7\\nFig. 120.\\ntions between brushes and commutator that may exist at\\nany instant. Both brushes of each set may rest on one\\ncommutator bar, or the brushes of one set may span the", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0165.jp2"}, "166": {"fulltext": "154\\nDYNAMO ELECTRIC MACHINERY.\\nbreak between two q\u00c2\u00a3 the bars. These conditions are re-\\npeated three times at each brush for each revolution. If\\nthe dotted line shows the position where the maximum\\nE.M.F. is generated in the coils, then in Fig. 121a the\\ntwo most active coils are connected in series with the out-\\nside circuit, while the coil near the position of least activity\\nis out of circuit. In Fig. 121b the two less active coils are\\nin multiple with themselves and in series with the most\\nactive coil and the external circuit. In practice the\\nFig. 121.\\nbrushes of a set are 60 degrees apart, leaving 120 degrees\\nbetween the leading brush of one set and the following\\nbrush of the other set and since 1 20 degrees is the angular\\nmeasure of the length of a commutator bar, there is no\\ncoil out of circuit at normal load, two-being always in\\nparallel and in series with a third. If the current rise\\nabove the normal the leading brushes move a small angle\\nforward, while the following brushes recede through three\\ntimes that angle. This will shorten the time that a single\\ncoil gives its whole E.M.F. to the circuit, and will place it\\nmore quickly in parallel with a comparatively inactive coil.\\nBut such a movement will reduce the angular distance be-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0166.jp2"}, "167": {"fulltext": "CONSTANT CURRENT DYNAMOS.\\n155\\ntween tne nearest brushes of the opposite sets to less than\\n1 20 degrees, hence the machine will be short circuited six\\ntimes per revolution, since one brush of each set will touch\\none segment of the commutator at the same time. If the\\ncurrent in the line falls below normal, then the brushes\\nclose together, and the time that a coil is in series is\\nlengthened, and the time that it is in parallel with an\\ninactive one is lessened.\\nUaaaaaaJ\\nHeld\\nCoi/s\\nFig. 122.\\nThe arrangement for moving the brushes is shown in\\nFig. 122. The leading brushes are shifted forward on an\\nincrease of current merely to help avoid sparking. The\\nbrushes are moved by levers actuated by a series magnet\\nA. This magnet is normally short circuited by the by-\\npass circuit. On an undue rise of current this circuit is\\nbroken by the series magnet B. A then becomes more\\npowerful, and the levers separate the brushes. While the\\nmachine is in operation the circuit-breaker C is constantly\\nvibrating, and brushes adjusting to suit the load. A high", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0167.jp2"}, "168": {"fulltext": "156 DYNAMO ELECTRIC MACHINERY.\\ncarbon resistance is shunted across C to prevent sparking\\nat that point.\\nAs might be expected, with but three parts to the com-\\nmutator and collection made with small regard to the\\nneutral point, the sparking of this machine is such as to\\nspeedily ruin the commutator and the brushes, if means\\nare not taken to suppress it. A rotary blower is mounted\\non the shaft, and is arranged to give intermittent puffs of\\nair, which at the right moment blow out the spark. The\\ninsulation between the segments is air, considerable gap\\nbeing left between them, and through these gaps the\\nsparks are blown.\\n85. Western Electric Arc Dynamo. Fig. 123 represents\\nthis machine, which is regulated by means of shifting the\\nbrushes. The brush and rocker are connected by means\\nof a link and a ball and socket joint with a long screw.\\nThis screw is held in position by a nut. When the current\\nis normal, both the nut and screw revolve at the same\\nrate, and consequently there is no end movement of the\\nscrew. The brush, therefore, remains stationary. An\\nelectro-magnet, energized by a coil which is in series with\\nthe main circuit, attracts an armature whose movement\\ntowards the magnet is opposed by the action of a spring\\nwhich is susceptible of regulation. When the current has\\ntoo high a value, the electro-magnet attracts its armature\\nmore strongly than ordinarily. The latter moves toward\\nthe magnet, and by its movement catches a stop on the re-\\nvolving nut, and thereby prevents the revolution of the nut\\nuntil the resulting longitudinal movement of the screw has\\nshifted the brushes sufficiently to bring the current to its\\nnormal value. If the current be too weak, the spring\\nwhich is attached to the magnet armature overpowers the", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0168.jp2"}, "169": {"fulltext": "CONSTANT CURRENT DYNAMOS. I 57\\nelectro-magnetic attraction. The resulting movement of\\nthe armature stops the rotation of the screw and permits\\nthe rotation of the nut. This results in a longitudinal\\nmovement of the screw and a shifting of the brushes in\\nthe opposite direction. The stopping and starting of the\\nnut and screw is accomplished through the medium of\\nFig. 123.\\nsmall triggers controlled by the armature of the series\\nmagnet. The triggers are fastened to a gear rotated from\\nthe main shaft by a belt. They engage with stops on the\\nnut and screw respectively.\\nFig. 124 gives a sectional view of the regulator, and the", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0169.jp2"}, "170": {"fulltext": "158 DYNAMO ELECTRIC MACHINERY.\\nFig. 124.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0170.jp2"}, "171": {"fulltext": "CONSTANT CURRENT DYNANOS.\\n159\\n^u", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0171.jp2"}, "172": {"fulltext": "160 DYNAMO ELECTRIC MACHINERY.\\ntrigger which engages with the screw is shown at n, and\\nthe one which engages with the nut is shown at m.\\nFig. 125 represents the details of the armature con-\\nstruction. The latter is ring wound with a large number\\nof turns in each section.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0172.jp2"}, "173": {"fulltext": "MOTORS. 161\\nCHAPTER IX.\\nMOTORS.\\n86. Principle of the Motor Any direct current dy-\\nnamo will act as a motor if supplied with current from some\\nexternal source. This source may be a constant E.M.F.\\nsystem, a constant current system, or any other system.\\nThe rotation of the armature is a direct consequence of the\\nconditions laid down in 20. It is evident that if the\\nnegative and positive terminals of a dynamo be connected\\nwith the corresponding terminals of some external source\\nof supply, the direction of flow in the armature will be\\nreversed. Irrespective of the multipolarity of the field or\\nof the method of armature winding, the electro-dynamic\\nactions between the field and all the currents in the in-\\nductors will conspire to produce rotation in one direction.\\n87. Direction of Rotation To determine the direction\\nof movement of an inductor carrying a current of known\\ndirection in a magnetic field of known direction, one may\\nemploy a modification of Fleming s rule. Thus in a dynamo\\nthe thumb and two first fingers of the right hand deter-\\nmine the direction of induced E.M.F. as shown in Fig.\\n1 26. But in a motor the thumb and two first fingers of the\\nleft hand can be made to determine the direction of motion\\nas shown in Fig. 127.\\nIf in a dynamo the direction of the field flux be not", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0173.jp2"}, "174": {"fulltext": "l62\\nDYNAMO ELECTRIC. MACHINERY.\\naltered, and if the armature be supplied with a current flow-\\ning in the same direction as when the machine was operated\\nas a dynamo, the direction of rotation will be reversed.\\nThus, if the positive brush of a dynamo be connected to\\nthe positive terminal of an external source of supply, and if\\nthe negative brush be connected to the negative terminal,\\nthen the direction of current flow in the armature will be\\nreversed. The direction of rotation of the armature, in\\ncurrehi\\nFIELD MAGNET\\nNORTH POLE.\\ni DYNAMO RIGHT HAND.\\nFIELD MAGNET\\nNORTH POLE.\\nMOTOR LEFT HAND/\\nFig. 126.\\nFig. 127.\\nseries-wound machines, since the field flux has its direction\\nalso changed, will be reversed. In shunt-wound, separately\\nexcited, and magneto machines, since these do not have\\ntheir fields reversed, the direction of rotation will be ten-\\naltered. Compound-wound machines will have the same\\nor reversed direction of rotation, depending upon whether\\nthe magnetizing effect of the shunt coils is stronger or\\nweaker than that of the series coils. In a compound gen-\\nerator the actions of the shunt coils and the series coils are\\ncumulative, i. e., in the same direction but when used as a\\nmotor the actions are differential, i. e., opposed to each other.\\nMotors are also wound so as to have cumulatively acting\\nseries coils.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0174.jp2"}, "175": {"fulltext": "MOTORS. 163\\n88. Speed Conditions If an electric motor be supplied\\nwith electrical energy, it will vary its rate of rotation until\\nit has attained such a speed as will produce an equality be-\\ntween the input of energy and the output of energy. The\\nlatter appears both as useful work and as losses. In the\\ncase of a motor, speed acts toward electrical energy like\\ntemperature in the case of heat energy. Temperature\\nalways rises until the heat energy which is produced is\\nequal to the heat energy which is disposed of by con-\\nduction, convection, and radiation.\\nThe electrical energy which is communicated to a motor\\nis transformed, a, into useful mechanical energy, which is\\ntaken from the armature shaft either by a belt or by direct\\nconnection b, into friction at the bearings and at the\\nbrushes; c, into windage; d into foucault and eddy currents;\\nand finally e, into ohmic heat energy in the motor s electrical\\ncircuits. The energy required per unit of time to overcome\\nfriction, windage, hysteresis, and foucault and eddy currents\\nincreases as the speed of rotation increases. Nearly all\\npractical loads put upon a motor machinery in one form\\nor another require an increase of power for an increase\\nof speed. Therefore, if a given amount of electrical power\\nbe communicated to a motor under load, the armature will\\nassume some speed of rotation, so that a balance between\\nthe input and the output of energy is maintained.\\n89. Counter E.M.F. If the variation of losses and useful\\nenergy with the speed were the only conditions governing\\nthe speed, then there would result in practice variations of\\nspeed through enormous ranges. But there is another con-\\ndition affecting the speed. The armature, by varying its\\nspeed, not only governs the rate of expenditure of energy,\\nbut also governs the amount of electrical energy received.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0175.jp2"}, "176": {"fulltext": "164 DYNAMO ELECTRIC MACHINERY.\\nThe armature of a motor revolving in a field under the\\ninfluence of supplied electrical energy differs in no respect\\nfrom the same armature revolving in a field under the in-\\nfluence of supplied mechanical energy. There is an E.M.F.\\ngenerated in it which is determined by the speed and quan-\\ntity of flux. For the same speed and the same flux there\\nwould be generated the same E.M.F. in the case of a motor\\nas in the case of a dynamo. The direction of this E.M.F.\\nis, however, such as to tend to send a current in a direction\\nopposite to that of the current flowing under the influence\\nof the external supply of E.M.F., according to \u00c2\u00a787.\\nTherefore this pressure which is induced in the armature of\\na motor is called counter electro-motive force. The current\\nwhich will flow through the inductors of an armature is\\ntherefore equal to the difference between the supply E.M.F.\\nand the counter E.M.F. divided by the resistance of the\\narmature, or\\nRa\\nFor example, an unloaded 1 k.w. shunt motor having an\\narmature resistance of 1 ohm, when connected to a con-\\nstant source of potential supply of 100 volts, would not take\\na current of 100 amperes as dictated by Ohm s law, unless\\nits armature were clamped so as to prevent rotation. If\\nundamped, its armature would assume such a speed that it\\nwould have induced in it a counter E.M.F. of say 97.5\\nvolts. The current then flowing in the armature would be\\n100 97. q\\n2.5 amperes.\\nThe power represented by this current, viz., 2.5 X 100\\nwatts, would all be expended in overcoming the losses of\\nthe machine.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0176.jp2"}, "177": {"fulltext": "MOTORS.\\n165\\n90. Armature Reactions Since in a motor, for a given\\ndirection of rotation and flux, the current in the armature\\nflows in a direction contrary to that\\nwhich it would have as a dynamo,\\ntherefore the effect of the motor\\narmature cross turns is to skew the\\nfield against the direction of rotation,\\nas in Fig. 128. Tnis increases the\\nmagnetic density in the leading pole\\ntip, and decreases it in the trailing\\ntip. This necessitates, for sparkless\\noperation, a backward lead, or a lag,\\nof the brushes. If the brushes were\\nin the same place as when the ma-\\nchine was operated as a generator,\\nthe direction of armature current\\nhaving been reversed, then the de-\\nmagnetizing or back turns of the\\ngenerator would become magnetiz-\\ning turns for the motor but with the brushes shifted to\\na position of lag, then the motor has also demagnetizing\\nor back turns.\\n91. Efficiency. In a compound- wound motor connected\\nto a constant pressure supply,\\nFig. 128.\\nLet R 8h resistance of shunt field coils,\\nR a S resistance of armature plus that of the series field\\ncoils,\\nV= number of revolutions per minute,\\nT torque given off at the pulley in pound feet,\\nE supply voltage,\\nI n no-load armature current in amperes, and\\narmature current when torque T is yielded.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0177.jp2"}, "178": {"fulltext": "1 66 DYNAMO ELECTRIC MACHINERY.\\nhence,\\nrTA1 __ useful power output\\n1 lie efficiency f\\nelectrical power input\\nrr VT 7 4 6\\n_ 2 7T Y 3 3\\nE 2\\nThe useful power can be expressed as the difference\\nbetween the power input and the losses. Now at no load,\\nwhen there is no useful power output, the following rela-\\ntions exist r\\nEI n -f power input,\\n-Ksh\\nand\\nI\u00e2\u0080\u009eR a s P f power in the armature and series coils.\\nAssuming the friction, the windage, the foucault current,\\nand the hysteresis losses to be constant and the same as\\nat no load, we have for their value a constant loss the\\nno-load power input the variable loss.\\nHence,\\nThe constant loss P f EI n -f- P sh P\\\\\\nwhere\\nP sh loss in shunt coils\\nThe efficiency under load will therefore be\\nEi p f rx a+s\\nEI P sh\\nIn a shunt motor R a+8 represents the armature resistance\\nonly hence,\\n_EI-P f -I 2 P a\\nIn a series motor P sh o hence,\\n_ Ei-p f -rp a+s\\nEI", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0178.jp2"}, "179": {"fulltext": "MOTORS.\\n167\\nIn the first of these three expressions for efficiency,\\nsolving for that value of which will give a maximum effi-\\nciency, we have\\nA (EI+P sh (E 2 IP a+s (EI-P f -n? a+s )E _\\ndl\\nwhence\\nEI+P*\\nI\\np., p A\\nP 2\\n\u00e2\u0096\u00a0*sh\\nE 2\\nPsh\\nE\\nFig. 129 gives a set of curves indicating the perform-\\nance of a motor whose fixed losses are large. Fig. 130\\nFixed/Losses in Shunt Coils, friction, foucault, and hysteresis.\\nPower Input\\nFig. 129.\\ngives a set of curves for an exactly similar machine save\\nthat the fixed losses are smaller. They might be con-\\nsidered as taken from the same machine as the first, but\\nwith journals better oiled, and hence with less friction loss.\\nThe difference in the efficiency curves is noticeable.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0179.jp2"}, "180": {"fulltext": "i68\\nDYNAMO ELECTRIC MACHINERY.\\nAbscissae in all cases represent power input. The ordi-\\nnate of P at any given load shows the power input at that\\nload. The constant ordinate of F represents the power\\nconsumed by the fixed losses, which is constant for all\\nloads. The ordinates of V, measured from F, follow the\\nFixed Losses in Friction, foucault, hysteresis and shunt coils,.\\nPower Input\\nFig. 130.\\nlaw PR a sy and represent the variable loss at various loads.\\nTherefore the total loss for any load is represented by the\\ntotal ordinate of Fat that load. The difference between\\nthe power input and the losses gives the useful power,\\nwhich is represented by the difference of the ordinates of\\nP and V. The values of the ratio for each\\npower input\\nload are plotted in the efficiency curve. Comparing the\\ncurves of the two machines, it is seen that to get a high\\nefficiency at full load the variable loss must be kept small,\\nwhile to obtain a good efficiency at small loads, the fixed", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0180.jp2"}, "181": {"fulltext": "MOTORS.\\n169\\nlosses must be made small. The shape of the efficiency\\ncurve can be controlled by a proper adjustrnent of the\\nrelation which exists between the fixed and the variable\\nlosses.\\n92. Starting Rheostats When the armature of a motor\\nis at rest there is no counter E.M.F.; and at the instant of\\nclosing the circuit a destructive current would flow if a re-\\nsistance were not first inserted in the circuit, except in the\\ncase of very small motors whose armatures have small\\nmoments of inertia. As the speed increases the resistance\\ncan be lessened without allowing too severe a current to\\nflow, and when full speed is obtained the resistance must\\nall be cut out to avoid loss. In order that counter E.M.F.\\nmay be generated from the start, the shunt field circuit\\nmust first of all be closed. These ends are obtained by the\\nuse of a starting-box or rheostat, the wiring of the ordinary\\ntype of which is shown in Fig.\\n131. Its main feature is a con-\\ntact arm pivoted at its center,\\nand revolving through almost\\n180 making various contacts.\\nThis arm is connected to one\\nterminal of the supply as shown.\\nAs it is slowly turned on, one\\nend of it first makes a connection\\nwhich completes the shunt field\\ncircuit. Then the other end\\nmakes a contact which closes\\nthe armature and series coils\\nthrough the maximum resistance\\nof the starting-box. As the\\nspeed increases, the revolving Fig I3I\\nShunt", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0181.jp2"}, "182": {"fulltext": "170\\nDYNAMO ELECTRIC MACHINERY.\\narm is made to cut out the resistance, piece by piece, until\\nit is finally all out of the circuit and the machine is run-\\nning independent of the starting rheostat.\\nFig. 132 shows such a starting-box as made by the\\nCrocker Wheeler Company. The brass contact points\\nand the arm are mounted\\non a slate slab, which\\nserves as the top of an\\nopen-work cast-iron box\\nwhich contains the resist-\\nances in the form of spiral\\ncoils of bare wire. The\\nwire is generally either of\\nGerman silver or of some\\none of the special iron\\nalloy resistance materials.\\nA shunt motor may\\nhave its armature coils\\ndestroyed by an excessive\\nrush of current resulting from a dropping or ceasing alto-\\ngether of the supply voltage followed by a sudden renewal\\nafter the speed of the armature has fallen. These condi-\\ntions may arise through accidents to mains or because of a\\ntoo heavy load on mains of insufficient cross-section. An\\narmature may also be burned out by an excessive cur-\\nrent due to overloading the motor. The resulting lower-\\ning of its speed is accompanied by a corresponding lowering\\nof the counter E.M.F. Again, a too high supply voltage,\\nwhich might result from some cross or other accident might\\ncause a destructive rush of current. To meet these condi-\\ntions, starting rheostats are often made with attachments\\nfor opening the circuit on no voltage or low voltage, and", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0182.jp2"}, "183": {"fulltext": "MOTORS.\\n171\\nRelease Magnet\\nFig. 133.\\nArmature,\\nFig. 134.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0183.jp2"}, "184": {"fulltext": "172\\nDYNAMO ELECTRIC MACHINERY.\\nothers with attachments for opening the circuit on overload.\\nSome have both attachments, but it is modern practice to\\nremove the overload attachment from the starting-box and\\nput it on the switchboard. Fig. 133 is a diagram of the\\nDetails of Release Magnet\\nm\\n4\\nu u\\ne e\\nFig. 135.\\nwiring of a starting rheostat for a shunt motor with auto-\\nmatic release and low-voltage attachment. Fig. 134 gives\\na front view of this same instrument. When the starting-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0184.jp2"}, "185": {"fulltext": "MOTORS.\\n173\\nhandle is placed in the on position, the magnet in the\\nfield circuit holds it there, although a spring tends to throw\\nit back. If now, because of low voltage, the current in field\\nand magnet becomes weak, the magnet is no longer able to\\ndetain the handle, and the spring throws it to the off\\nposition, where it stays until the motor is again turned on\\nby an attendant.\\nFigs. 135 and 136 show a view and a diagram of the\\nwiring of a rheostat with both release and overload attachi-\\nng. 136.\\nments. The former is similar to the one just described,\\nwhile the overload attachment consists of a magnet in the\\narmature circuit which on overload becomes strong enough\\nto attract to itself a pivoted iron arm supplied at its end\\nwith a device which short circuits the field current around", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0185.jp2"}, "186": {"fulltext": "174\\nDYNAMO ELECTRIC MACHINERY.\\nthe release magnet. This causes the latter to let the\\nstarting-handle drop as in the case of low voltage.\\n93. Characteristic Curves of a Shunt Motor A shunt\\nmotor, having a small R a and a large R shi and having the\\nfield well saturated, will give a fairly constant speed under\\nall loads, if supplied from a constant pressure circuit.\\nThis is shown by the curves in Fig. 137, which are from\\na bipolar, shunt-wound, 10 horse-power, 230-volt Crocker\\nWheeler motor.\\nA shunt motor when\\nstarted cold on no load\\nquickly arrives at a speed\\nwhich then gradually\\nrises to a maximum. The\\ngradual heating of the\\nfield coils increases their\\nresistance. This allows\\nless current to flow in\\nthem, and the resulting\\nmagnetic flux is less.\\nTherefore the armature\\nmust rotate faster to gen-\\nerate the same counter E.M.F., as explained in 89.\\n94. Compound- Wound Motors In silk-mills and other\\ntextile factories where any slight variation in the speed\\naffects the character of the manufactured product, com-\\npound motors give a satisfactorily constant speed. The\\nobject of the compounding coils is to weaken the flux in\\nthe armature as the load increases. If, at a given load,\\nunder the influence of shunt excitation alone, the speed\\n100\\n90\\no\\nI 70\\nu.\\nu 60\\n\u00c2\u00a750\\nHI\\n^40\\no\\n10\\nSF\\nEE\\nD\\n9(\\nu\\n-J\\nr^\\n4?\\ncy\\nj\\nW\\nS\\nEFFICIENCY, SPEED.\\nTORQUE CURVES\\nSIZE tOC. 230 V.\\nBI-POLAR SHUNT MOTOR\\nCROCKER-WHEELER COMPANY\\nc\\nUT\\n=ut 1^1 ^or!se-|po^ep 1 485\\n100\\n70s\\nt\\n60\\nCO\\n50 I\\n1-\\n40 1\\n30 o\\n20 1\\no\\n10\\n4 6 8\\nFig. 137.\\n.10 12 14", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0186.jp2"}, "187": {"fulltext": "MOTORS.\\n175\\nwould fall a certain per cent of the speed at no load, then\\nthe armature flux must be lessened by the same percentage\\nin order to bring the speed up to its original value. In\\ncalculating the number of series turns, account must be\\ntaken of the fact of\\nmagnetic leakage,\\nsince the regulating\\ncoils are on the field\\nmagnets and not on the\\narmature direct. Cu-\\nmulatively compound-\\nwound motors are used\\nin order to obtain a\\nlarge starting torque.\\nThe influence of the\\nseries coils is not very\\nattained.\\nShunt Field\\nFig. 138.\\ngreat after full speed has been\\n95. Hand Speed Regulation A rheostat placed in the\\nfield circuit of a shunt motor can be used to vary the\\nspeed of the motor at will, as in Fig. 138. An increase\\nof the resistance will decrease the current in the field\\ncoils. As a result the armature magnetic flux will decrease\\nand hence the speed will increase. If the fields be pretty\\nwell saturated, it will require a resistance of some con-\\nsiderable size, say twice as large as the field resistance, to\\ncut the current down enough to materially reduce the\\nflux and increase the speed. Motors of older make seldom\\nhad fields magnetized anywhere near saturation. There-\\nfore they are very susceptible to the slightest change of\\nresistance in their field circuits. If the demagnetizing\\narmature ampere turns be large, it is possible for a motor", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0187.jp2"}, "188": {"fulltext": "176\\nDYNAMO ELECTRIC MACHINERY.\\nSeries R.\\n^wwvw\\\\\\nSource\\nField Coils\\nFig. 139.\\nto increase its speed under increase of load. This is due\\nto the decrease of armature flux.\\n96. Speed Regulation by Series Resistances. The\\nspeed of a motor on a constant pressure circuit can easily\\nbe varied over a wide range,\\nfrom rest to full speed, by\\nmanipulating a resistance\\nin series with it. The use\\nof this method is not to\\nbe advised save for ex-\\nperimental purposes, since\\nit is very wasteful of en-\\nergy. The I 2 R loss in\\nthe regulating resistance\\nis sometimes considerably\\nmore than the power actually used. Fig. 139 shows the\\nwiring for this style of regulation.\\n97. The Leonard System of Motor Speed Control This\\nsystem is especially advocated for use in operating elevators,\\ncranes, battleship turrets, and all equipments requiring a\\nthorough control of the speed and precision of stoppage.\\nFig. 140 shows the arrangement of such a system. M is\\na motor whose field is separately excited all the time from\\na source of constant potential, E. G is a dynamo which\\ngenerates power for the armature of motor M. The arma-\\nture of the dynamo G is maintained at approximately con-\\nstant speed by the prime mover S, which may be a steam\\nengine or a motor run by power taken from the source E.\\nThe generator G is separately excited by current derived\\nfrom E and controlled by the reversing rheostat C.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0188.jp2"}, "189": {"fulltext": "MOTORS.\\n177\\nWhen it is desired to start the motor, the field of the\\ngenerator is weakly excited by moving the controller so\\nthat a high resistance is in circuit with the field. This\\ncauses the dynamo to send current of low potential to the\\narmature of the motor M. The latter then starts to move\\nslowly. To accelerate the speed, more resistance is cut\\nout of the controller. The pressure of the current supplied\\nto the motor armature simultaneously increases and with\\nit the motor s speed. Since the power represented by\\nthe current required to excite the field of G is at most\\nFig. 140.\\nbut a small fraction of the useful power given out by the\\nmotor, the I 2 R loss in the resistance C is very much less\\nthan would be the loss in a series regulating resistance as\\ndescribed in the last section. It is claimed that the extra\\nfirst cost of this system is offset by the decreased cost of\\nrepairs, since violent stresses and bad sparking are avoided.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0189.jp2"}, "190": {"fulltext": "178 DYNAMO ELECTRIC MACHINERY.\\n98. Slow-Speed Motors It is a practical advantage to\\nhave a motor connected directly to the machine it is to\\noperate, without the intervention of belting or reducing\\ngears. Slow speed is also of advantage where absence of\\njarring is desired or where many stops and starts are to\\nbe made. Slow speed can always be obtained from an\\nelectric motor but it is generally expensive, since the\\nnatural speed of motors as well as of dynamos is high. In-\\ncrease of magnetic flux and increase of armature diameter\\nis necessary to obtain slow speed. The increase of ma-\\nFig. 141.\\nterial increases both the first cost and the losses during\\noperation.\\nThe power of a motor is its torque or turning moment\\nmultiplied by the number of revolutions hence for the", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0190.jp2"}, "191": {"fulltext": "MOTORS.\\n179\\nsame output of work, a machine making half as many\\nrevolutions as another must have twice the turning mo-\\nment. These conditions make it imperative that the ma-\\nterials of construction, both iron and copper, be worked at\\nmaximum magnetic and current densities respectively, in\\norder to economize in first cost and weight. In general\\nthe efficiencies of low-\\nspeed motors do not\\ncompare favorably\\nwith those of motors\\nhaving a higher speed.\\nFig. 141 is a cut of a\\nCrocker Wheeler eight-\\npole, direct current\\nmotor for direct connec-\\ntion. It will furnish 2\\nhorse-power at 100 rev-\\nolutions per minute, 4\\nhorse-power at 200 R.\\nP.M.,, and the quotient\\nof its speed per minute\\nby its full load horse-\\npower is equal to the\\nconstant quantity 50. Its efficiency increases as the\\nspeed according to the curves shown in Fig. 142.\\nyy-\\nI I\\nLOAD\\nUjfa[\u00c2\u00a9\\n70\\npr\\nLOAD\\nI\\n60\\nVi LOAD\\nz\\nf s*\\nP\\n50\\nT\\nQ.\\n-z-\\nI\\n40\\nn\\nz\\nUl\\nI\\nEFFICIENCY AT\\nVARIOUS SPEEDS OF\\nSIZE 2-100 MOTOR.\\nCROCKER-WHEELER\\nELECTRIC CO.\\nAMPERE, N. J.\\n30\\nu.\\nHI\\n1\\n20\\n1\\n10\\nSPEED-R\\nEV.\\n3 E*\\nMl\\na.\\n87\\n100\\n200 300\\nFig. 142.\\n400 500 600\\n99. Brake Motors. For cranes, elevators, and hoists,\\nwhere it is necessary to hold the load after raising it, and\\nfor looms and printing-presses, where it is important to\\nsecure a sudden and accurate stop instead of a gradual\\nslowing down, it is desirable to use motors with a brake\\nattachment. A brake operated by hand or foot requires", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0191.jp2"}, "192": {"fulltext": "i8o\\nDYNAMO ELECTRIC MACHINERY.\\ncareful operation lest it be applied too soon and injure the\\nmachine, or too late and allow the load to fall some hence\\nan automatic brake is desirable.\\nFig. 143 shows the construction used by the Crocker\\nWheeler Company. One of the pole pieces is pivoted at\\nits base, and thus has a slight motion to or from the arma-\\nture. It is normally held from the armature by a heavy\\ncoil spring, and in this position tightens the brake band.\\nThe moment that current is allowed to pass through the\\nfield coils, the poles attract each other, overcoming the\\n1\\n2J\u00c2\u00a7l)\\nk\u00c2\u00b0j j\\nWo-Ji J\\nOFF\\nON\\nFig. 143.\\nresistance of the spring, and the brake band is thus loosened.\\nThe spring and band may be adjusted to allow a few revo-\\nlutions before stopping, or the armature may be clamped\\nthe instant current is turned off. In the latter case, if\\nconnected to heavy machinery, shafting or gearing may be\\nbroken.\\nStrap brakes are cumulative in their action the friction\\non the free end of the brake against the drum tightens\\nthe whole brake, thus increasing its effect. This action is", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0192.jp2"}, "193": {"fulltext": "MOTORS.\\nISI\\nonly obtained when the motion of the drum is away from\\nthe fixed end. To obtain powerful brake action, therefore,\\non motors that run either way,\\nas in elevator motors, a reversing\\nbrake is employed. This is op-\\nerated by the movement of one\\npole piece as before, but the ends\\nof the brake band are attached\\nto a system of links and levers\\nso that either end may become\\nthe fixed end. This construction\\nis shown diagrammaticallyin Fig.\\n144. When the brake is applied,\\nthe friction causes the whole\\nband to follow the drum until the sliding link attached to\\none or the other end of the band is held by the stud. The\\nother, or free, end of\\nthe band, is tightened\\nby the pull of the lev-\\ners on one of the\\nsmaller straps attach-\\ned to the brake band\\nas shown. Fig. 145\\nshows a one horse-\\npower Crocker Wheel-\\ner motor fitted with\\nreversing brake.\\nIn multipolar ma-\\nchines it is imprac-\\nticable to employ a\\nmoving piece, and in\\nFig. 145. lar e bi P olar ma", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0193.jp2"}, "194": {"fulltext": "182\\nDYNAMO ELECTRIC MACHINERY.\\nchines it is undesirable to interrupt the magnetic circuit\\nby a pivot joint; hence a solenoid brake is employed. This\\nis simply a spring actuated friction brake kept norm-\\nally in engagement. On current being supplied to the\\nmachine a solenoid acts to release the brake. The opera-\\ntion of this type is clearly seen by inspecting Fig. 146.\\nFig. 146.\\nAn objection to this type of automatic brake is that it\\nconsumes electrical energy all the time that the machine is\\nin motion.\\n100. Recording Meters. The recording watt-hour meter,\\nFig. 147, is coming into extensive use, both as a station in-\\nstrument and as a measurer of the quantity of energy\\nsupplied to individual consumers. It is a very delicately\\nadjusted compound-wound motor, having no iron in its\\nmagnetic circuit. When a current flows, the time integral", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0194.jp2"}, "195": {"fulltext": "MOTORS.\\n183\\nof the watts or power is registered, by means of a train of\\nwheels operated by the armature, on a dial similar to that\\nof a gas-meter. The connec-\\ntions for such a meter are\\nshown in Fig. 148. The ar-\\nmature is connected in series\\nwith a high resistance across\\nthe service wires hence the\\ncurrent flowing in the arma-\\nture is proportional to the\\nvolts of the supply. The\\nfield coils are in series with\\nthe service, giving a field\\nstrength proportional to the\\ncurrent, and the motor effort\\nis proportional to the product of the two or to the watts\\nsupplied. The shunt field coils are added to compensate\\nfor the friction of the moving parts. Since a small cur-\\nrent is always flowing in the armature, as well as in the\\nFROM GENERATOR\\nFig. 147.\\nc 5\\n3 -a\\n2 5\\nMains\\nFig. 148.\\nshunt field coils, the motor is always slightly excited, and\\nby regulating the number of shunt turns the amount of", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0195.jp2"}, "196": {"fulltext": "184 DYNAMO ELECTRIC MACHINERY.\\nthis excitation is adjusted so that at no load on the service\\nwires the armature almost, but not quite, moves. If it\\nwere not for this constant excitation, a small, though\\ncontinuous, current could be drawn off the mains without\\noperating the recording mechanism because of its friction.\\nTo control the speed a copper disk is mounted on the\\narmature shaft and between the poles of two or more\\nadjustable and permanent horseshoe magnets. When the\\narmature revolves, Foucault currents are set up in this\\nplate, and cause the proper retardation. By moving the\\npoles of these horseshoe magnets from the center to the\\ncircumference of the disk, a variation of about 16 per cent\\nin the speed for a given watt consumption can be effected.\\nAdvantage is taken of this fact in adjusting the instru-\\nments. The more important bearings are constructed of\\njewels, such as are used in watches, and the whole machine\\nis carefully protected from dust. When the instrument\\nis in a position where it is subject to jars or vibrations\\nthat reduce the friction of standing to such a point that\\nthe constant excitation causes the armature to revolve a\\nlittle, the machine is said to creep. The remedy is\\nto mount on a rubber or other non-vibrating base, or to\\nreduce the number of shunt field turns.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0196.jp2"}, "197": {"fulltext": "SERIES MOTORS. 185\\nCHAPTER X.\\nSERIES MOTORS.\\n101. Series Motors. When subjected to a heavy load on\\nstarting, that is when there is a heavy current at a very low\\nspeed, a series-wound machine is far superior to one that is\\nshunt-wound. For work that requires good effort at widely\\ndifferent speeds the series motor is particularly adapted.\\nFor this reason series-wound machines are used on electric\\nrailways, for crane motors, for ammunition and other hoists,\\nfor mill motors, and in all other places where a good effort\\nis required at a varying speeds. A series-wound machine\\ncan be used on either a constant current circuit or on a con-\\nstant potential circuit but a series motor is seldom run on\\na constant potential circuit unless it is directly or very\\nsolidly coupled with its load, as in the case, for instance,\\nof a railroad motor. If connected by means of a belt,\\nand if the belt should break off or slip off, the motor would\\nrace and damage might result. This difficulty does not\\npresent itself when series motors are used on a constant\\ncurrent circuit.\\n102. Series Motors on Constant Potential Circuits. As\\nin the case of a shunt motor, on a constant pressure\\ncircuit, the armature speed of a series motor will increase\\nuntil it reaches a value where the counter E.M.F. cuts\\ndown the armature current to such a point that the total", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0197.jp2"}, "198": {"fulltext": "1 86\\nDYNAMO ELECTRIC MACHINERY.\\nelectric power, (IE), received by the motor, is equal to the\\nsum of the fixed losses, the variable losses, and the useful\\nmechanical power. With a shunt-wound motor, a very\\nsmall variation of speed is sufficient to compensate for a\\nwide variation of load. A series motor tends to increase\\nits speed on removal of the load, as in the case with shunt\\nmotors. It in this manner increases the counter E.M.F.\\nThe resulting decrease of current results, however, in a\\nweakening of the field,\\nand as a consequence ad-\\nditional speed is required\\nto maintain the E.M.F.\\nThus a small change in\\nload results in a wide\\nchange of speed in a series\\nmotor. For a series-\\nwound mill motor, the\\nrelations which exist be-\\ntween speed, current, and\\nuseful torque (turning mo-\\nment) are shown in Fig.\\n149. There is also given\\na curve of the efficiency of the machine including gear-\\ning. It is evident that if, while the motor is at rest,\\nthe circuit be closed, an enormous rush of current would\\noccur, giving an enormous torque. Destructive heating\\nand sparking would probably result. To prevent damage\\nit is therefore necessary, in the operation of these motors,\\nto insert a series resistance at the start which may be cut\\nout after the speed has risen enough to give a sufficient\\ncounter E.M.F. In practice controllers are used as de-\\nscribed later.\\n100\\n90\\n80\\no\\n170\\nu\\n5 60\\n\u00c2\u00a750\\no\\nu\\ny 30\\n^20\\n10\\nEFFICIENCY,\\nSPEED AND\\nTORQUE CURVES\\nSIZE 14 280 V.\\nMILL MOTOR SERIES WOUND\\nCROCKER-WHEELER COMPANY\\ni\\n\u00e2\u0096\u00a0350\\n1\\n1\\nX\\nw\\n1\\nj{\\nr\\nL_\\nD\\n-250-\\n1\\n4\\ny\\nIS\\nV\\n7\\n^N\\nv\\nO\\nili\\nO\\n~6\\nt\\nftt\\nN\\nE\\ni\\n\u00c2\u00a3z.\\nV\\nj\\n11\\n)V\\nV\\nAM\\nPERES IN 1\\nPU\\nT\\n4\u00c2\u00a3\\nO\\n10 20 30 40 50 60 70\\nfig. 149.\\n10C0\\n900\\n800\\nto\\na\\n700 t\\n600 t\\n500 I\\n1-\\n400\\no\\n300\\nin\\n200\\no\\n100", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0198.jp2"}, "199": {"fulltext": "SERIES MOTORS. 187\\n103. Railroad Motors Experience has shown that\\nseries motors operating on a constant potential circuit of\\n550 volts, furnish a very satisfactory motive power for the\\npropulsion of trolley street-cars and electric railroad motor-\\ncars. At the time of this writing there are nearly two\\nmillion horse-power of street-car motors in service in this\\ncountry. The railway motor has been developed to a high\\ndegree of perfection during recent years, and is reasonably\\nwell fitted to meet the many requirements that are found\\nin this service. A railway motor must be mechanically\\nstrong to withstand the excessive hammering to which it\\nwill be subjected when in service. Rough tracks and bad\\nswitches are usual in trolley road beds. When satisfactor-\\nily geared to the wheel axle, the motor can be suspended\\nby springs on one side only, the other side being of neces-\\nsity mounted directly on the axle. Railway motors are\\nalso subject to abuse at the hands of the motormen. The\\nseries resistance is often cut out rapidly before the car has\\nan opportunity to accelerate. As a result there is an enor-\\nmous current and torque with little speed. This severely\\nstrains the motor and is particularly liable to disturb the\\narmature windings. The motor must be either weatherproof\\nof itself or incased in a weatherproof shell, because of the\\nmud, the water and the slush through which cars must\\noften run. Furthermore a railway motor should permit of\\nquick, convenient, and accurate alignment of parts and\\nadjustment of the intermediate driving mechanism.\\nThe method of suspending the motors from the trucks\\nis a matter of considerable importance. In practice four\\nstyles of suspension are used, viz., the side bar, the cradle,\\nthe nose, and the yoke suspensions. In every case one\\nend of the motor frame contains bearings which run on", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0199.jp2"}, "200": {"fulltext": "DYNAMO ELECTRIC MACHINERY.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0200.jp2"}, "201": {"fulltext": "SERIES MOTORS.\\n189", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0201.jp2"}, "202": {"fulltext": "190\\nDYNAMO ELECTRIC MACHINERY.\\nthe wheel axle and keep the pitch circle of the armature\\nshaft pinion always tangent to the pitch circle of the gear\\nwhich is mounted on the axle. The side-bar suspension,\\nshown in Fig. 150, consists of two parallel side-bars which\\nare mounted on the truck through heavy springs, and\\nwhich support the motor in the line of its center of gravity.\\nThe motor-axle bearings are thus relieved of the weight of\\nthe motor, and the latter is held without undue strains.\\nFig. 153.\\nThe cradle suspension, Fig. 151, is very similar to the side\\nbar, the difference being that the two side bars are replaced\\nby one U-shaped piece. This, at its curved end, is mounted\\nflexibly on a part of the truck frame which in turn is\\nmounted on the truck through springs. The nose suspen-\\nsion, Fig. 152, does not hold the machine at its center of\\ngravity, but part of the weight is thrown on the motor-\\naxle bearings. The rest is suspended from a spring-\\nmounted member of the truck bv a link, bolted to a nose", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0202.jp2"}, "203": {"fulltext": "SERIES MOTORS.\\n191\\ncast in the motor frame. The yoke suspension, which is\\nthe least flexible of all, differs from the nose suspension in\\nthat the link is dispensed with and the spring-supported\\nmember of the truck is bolted rigidly to the motor frame.\\nThe cradle-suspension type is advocated by the Westing-\\nhouse Company, the yoke or nose by the General Electric\\nCompany. The size or style of truck frequently requires a\\nparticular type of suspension.\\nFig. 154.\\nA GE-67 railway motor, made by the General Electric\\nCompany, is shown in Figs. 153 and 154. This machine\\nwill develop 38 horse-power when operated on a 500-volt\\ncircuit without heating more than 75 C. above the sur-\\nrounding atmosphere after one hour s run. The magnet\\nframe is hexagonal, with rounded corners, and is cast in\\ntwo pieces from soft steel of high permeability. The\\nparts are hinged together so that the lower part may be", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0203.jp2"}, "204": {"fulltext": "192\\nDYNAMO ELECTRIC MACHINERY.\\nswung down for inspection or repairs (Fig. 155). The up-\\nper part has cast on it two lugs, shown clearly in Fig. 153,\\npierced with two holes each for bolting to the yoke. Nose\\nsuspension can, however, be substituted. A covered opening\\nover the commutator permits removal of the brushes with-\\nout disturbing the rest of the machine. The bearings,\\nboth for armature shaft and for axle, consist of cast-iron\\nFig. 155.\\nrings or shells, with Babbitt metal swaged into them, and\\nare arranged for lubrication by both oil and grease. The\\noil is supplied to the shafts by felt wicks leading from oil-\\nwells. The grease is fed through a slotted opening in the\\ntop of each bearing from a grease-box directly over each\\nbearing, and means is provided for the passage of the\\nlubricant from the bearing after it has been used. The\\narmature bearings are 3 x 8 at the pinion end and 2f x", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0204.jp2"}, "205": {"fulltext": "SERIES MOTORS. 193\\n6\\\\ at the commutator end. The motor-axle bearings are\\neach 8 long. The pole pieces are built of soft iron lam-\\ninations, riveted together, and are securely bolted into\\nplace on the magnet frame. The coils are spool wound,\\nand are held in place by steel flanges. These magnetically\\nimperfect constructions are rendered necessary by the\\nsevere service the machine is expected to stand.\\nThe armature is built up of thin, soft iron laminations,\\njapanned, and keyed to the shaft. At each end is a cast-\\niron head, also keyed to the shaft. The core is hollow,\\nventilation being effected by air which enters at the pinion\\nend and passes out through ventilating ducts left in the\\nlaminations. The winding is of the series drum type, in\\ncoils being used, which are connected to a commutator of\\nin segments. The number of turns to a coil depends\\nupon the class of service the motor is to render. The\\ncoils are made up of sets of three, each set being sepa-\\nrately insulated before being placed in the slots. The\\ncoils are firmly secured in place by tinned steel wire bands\\nheld by chips and soldered together. Where the windings\\ncross the ends of the core, they are protected by canvas.\\nOn the pinion end, a projecting flange protects the wind-\\nings from injury by careless handling. The brushes slide\\nradially in finished ways in a brass brush holder, and\\nare held in contact by independent pressure fingers. All\\nthe leads to the motor pass through rubber-bushed holes\\nin the front of the magnet frame. The pinion has a taper\\nfit on the armature shaft. It, as also the gear on the axle,\\nis made of steel, and has teeth of face and 3 pitch.\\nWhen mounted properly on a truck with the ordinary 33-\\ninch wheels, there is 4^ clearance between the bottom of\\nthe motor and the top of the rails. The shapes of the", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0205.jp2"}, "206": {"fulltext": "194 DYNAMO ELECTRIC MACHINERY.\\ndifferent parts of this motor are well shown in the exploded\\nFig. 156.\\nA motor for railway service, very similar in design to\\nthe one just described, is No. 49, made by the Westing-\\nhouse Electric and Manufacturing Company. This motor,\\nshown in Fig. 157, has a weather-proof cast -steel frame,\\nhinged to open in a horizontal plane through its center,\\nand having a hand-hole above and one below the com-\\nmutator. The upper half is cast with lugs for side-bar or\\ncradle suspension, and also with a lug for nose suspension.\\nThe pole pieces are of laminated soft iron, are four in\\nnumber, and are secured to the frame by having the latter\\ncast around them. The lathe-wound field coils are secured\\non the pole pieces by brass castings, which are bolted to\\nthe frame.\\nThe armature is of the slotted drum type, having a\\nlaminated core with three ventilation passages parallel to\\nthe shaft. The coils are wound on formers, insulated in\\nsets of two, and then applied to the core. This armature\\nis constructed as light and as small in diameter as is prac-\\nticable, for the double reason of decreased centrifugal\\nstrain on the armature coils and decreased wear on the\\nparts in stopping the car. When the motor is started,\\nenergy is stored in the armature and other revolving parts,\\nas in a fly-wheel and when the car is stopped, this energy\\nis wasted, and causes wear and tear on the pinions and\\nbearings. In street-car service, where stops are frequent,\\nthis loss and this wear is by no means inconsiderable.\\nHence the armature of a street-railway motor should not\\nbe built with a great fly-wheel capacity. The high speed\\nof car-motor armatures makes the operating expenses for\\ncar acceleration and retardation considerable.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0206.jp2"}, "207": {"fulltext": "SERIES MOTORS.\\n195", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0207.jp2"}, "208": {"fulltext": "196\\nDYNAMO ELECTRIC MACHINERY.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0208.jp2"}, "209": {"fulltext": "SERIES MOTORS. 197\\n104. Controllers. It is general practice to equip each\\ntrolley car with at least two motors, and to regulate\\nthe speed of the car in the following manner First, the\\ntwo motors and a resistance are connected in series. The\\nresistance is then cut out step by step until the two motors\\nare operating in series on 500 volts. Since, with all the\\nMOTOR 1 MOTOR 2.\\nRl ^2 R3 ARMA. FIELD ARMA. FIELD\\nL/ \\\\m vw\\\\i m o\u00c2\u00bb\u00e2\u0080\u0094 owf^ K\\n-WP-t-Wh Wi 01 ow\u00e2\u0080\u0094\\n-m ww^-Wv ofh ow\u00e2\u0080\u0094\\nRUNNING),\\nN0TCH AAU MM, AAAA^l\\n\u00e2\u0080\u0094ww m a/w\\\\t-^ w\u00e2\u0080\u0094 ow-\\nRUNNING\\nNOTCH\\n-w\u00c2\u00bb wyv wP^of%- fiSMy\\nlvvw| vwwi\\nhm^-mam vw\\\\^---H y w^r\\n-m m^M/W\\\\r~K ^K W-r\\n8 -Ww wyL wj^jLj^y^ ^L*^^\\nrunning;\\nRUNNING)\\nNOTCH\\n\u00e2\u0080\u0094WA WW m Jt -K 1 K fJ%*\\nFig. 158.\\nresistance cut out, there is no unnecessary I 2 R loss, this is\\ncalled a running connection, and the controlling mechanism\\nis said to be upon a running point. To further increase\\nthe speed, the motors are placed in parallel with a resist-\\nance in series with both. This resistance is then cut out\\nstep by step until the motors are each operating on 500\\nvolts. This, again, constitutes a running connection. A\\nfurther change is sometimes effected by placing a small", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0209.jp2"}, "210": {"fulltext": "198 DYNAMO ELECTRIC MACHINERY.\\nresistance in shunt with the fields when all the series re-\\nsistance is out. This reduces the field flux, and causes a\\nhigher armature speed to maintain the necessary counter\\nE.M.F. A car governed in this way has four running\\nconnections. On heavy cars, such as are used in elevated\\nrailway or inter-urban service, four motors are used on\\neach car. In this case, the motors are governed in two\\nseries-parallel combinations, as if there were two separate\\ncars governed by one controller. The connections for a\\ntwo-motor car having nine speeds, a three-part series re-\\nsistance, and a field-shunt resistance, are shown diagram-\\nmatically in Fig. 158.\\nThe different connections are made by a motorman, who\\noperates a handle on top of a controller. Each different\\ncombination is called a. point or a notch. A pointer affixed\\nto the controller handle indicates at what notch the car is\\nrunning. Running points are indicated on the controller\\ntop by longer marks than the resistance points. A con-\\ntroller is almost invariably placed at each end of the car.\\nFig. 159 shows the interior of a General Electric\\nCompany s k-10 series parallel controller. The wires\\nfrom the trolley, from the fields, from the armature, and\\nfrom the different terminals of the series and shunt re-\\nsistances are brought up under the car to terminals on a\\nconnecting-board in the bottom of the controller. On\\nthis connecting-board there are also switches, one for each\\nmotor. These enable one to cut out an injured .motor\\nwithout interfering with the operation of the other motor\\nor motors. From the connecting-board conductors are\\nrun to terminals, called fingers or wipes. Mounted on an\\ninsulating cylinder, which may be revolved by the con-\\ntroller handle, are insulated contact pieces, which at various", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0210.jp2"}, "211": {"fulltext": "SERIES MOTORS.\\n199\\nangular positions of the cylinder make electrical connec-\\ntions between various wipes, and give the proper con-\\nnections for the various points or notches. A\\nFig. 159.\\nsmaller cylinder connected to a reversing-lever, is situated\\nto the right of the main cylinder. This has contact pieces\\nwhich are arranged so as to enable the motorman to re-\\nverse the direction of rotation of both motors or to cut\\nthem out entirely. Interlocking devices are supplied so", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0211.jp2"}, "212": {"fulltext": "200 DYNAMO ELECTRIC MACHINERY.\\nthat the reversing handle cannot be moved unless the con-\\ntrolling handle is in such a position that connection with\\nthe trolley is broken. The controlling handle also cannot\\nbe moved, if the reversing handle is not properly set either\\nto go forward or to go backward. The reversing handle\\ncannot be removed from the controller, save when the\\nsmaller cylinder is in the position that cuts out both motors.\\nAs serious arcs are liable to develop upon breaking a\\ncircuit of 500 volts, the contact pieces and wipes are sepa-\\nrated from adjacent ones by strips of insulating material\\nwhich are fastened to the inside of the controller cover,\\nand which fold into place when the cover is closed. These\\nare to be seen at the right of the figure. The power\\nshould never be turned off by a slow reverse movement of\\nthe controller handle, as destructive arcs are liable to\\noccur upon a slow break. To lessen the speed of a car,\\nthe power should be completely and suddenly shut off.\\nBefore the car has slackened its speed too much the con-\\ntroller handle can be brought up to the proper point. The\\narcs, which form upon disconnection at the fingers, are\\npretty effectively blown out by the field of an electro-\\nmagnet whose coil is above the connecting-board at the\\nright.\\n105. Motors For Automobiles. For electric automo-\\nbiles the series-wound motor is invariably employed. A\\nstorage battery of 40 or 44 cells is the customary source\\nof power for these motors. The use of these cells affords\\na convenient and economical means of speed control. In\\nthe case of a single motor, for the first controller notch,\\nthe cells may be connected in four-series groups of 10 or\\n11 each, giving about 22 volts, the four groups being con-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0212.jp2"}, "213": {"fulltext": "SERIES MOTORS. 201\\nnected in parallel. Other notches would correspond to\\nother series parallel combinations, and finally the last and\\nhighest speed notch would correspond to a connection of\\nall the cells in series. By this arrangement one cell is\\nused just as much as any other, and they are discharged at\\nequal rates. As the voltage supplied to the motor is\\nvaried without recourse to a series regulating resistance,\\nthere is no useless PR loss in starting or running at less\\nthan full speed. Often a series parallel control is employed\\nwhen two motors are used. It is also common to use two\\n37^ volt motors connected permanently in series and con-\\ntrolled as one motor.\\nThe advantage of using two motors on an automobile is\\nthat each may drive a wheel, allowing independent rota-\\ntion on turning curves, while if one motor only is used\\nsome form of differential gear must be employed to allow\\nfor sharp turns. But the efficiency of one motor is in\\ngeneral greater than the efficiency of two motors of half\\nthe power, and the gain in efficiency by using one motor\\nmore than balances the cost and complication of a differ-\\nential gear.\\nThe question of efficiency in these motors is of great\\nimportance, for practice has shown that it is profitable to\\npurchase i per cent efficiency, even at the cost of 10 per\\ncent increase of motor weight. This is because the ratio\\nof the battery weight to the motor weight is such that a\\ndecrease of i per cent in the capacity of the battery re-\\nduces its weight more than 10 per cent of the motor\\nweight. Since lightness is a prime object, only the very\\nbest materials can enter into the construction of a suc-\\ncessful automobile motor. The magnetic circuit must be\\nof material of the highest permeability. Ball bearings are", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0213.jp2"}, "214": {"fulltext": "202 DYNAMO ELECTRIC MACHINERY.\\nnot infrequently used in the shaft bearings, but their lia-\\nbility to wear and the consequent regrinding is an objec-\\ntion.\\nIt is general practice to rate these motors at 75 volts, or\\n37^ volts if two are used. Since 40 or 44 cells of battery in\\nseries can fall to 75 volts without injury, this is the lowest\\npressure on which the motors will be expected to run for\\nany length of time at full speed. Hence this voltage is\\nused as the basis for rating. For the best motors the\\nrating is for a temperature rise of 50 or 6o\u00c2\u00b0 C. on an in-\\ndefinite run. A motor so rated will carry 100 per cent\\noverload for half an hour, 150 per cent for ten minutes, and\\na momentary overload of 400 or 500 without overheating\\nor damage to the insulation.\\nThe battery of 40 or 44 cells is well adapted to automo-\\nbile purposes. It can conveniently be made to have the\\nrequired capacity, and it may be charged from any 115-\\nvolt direct current, incandescent lighting circuit with very\\nlittle resistance in series and hence a small PR loss.\\nAlthough the voltage of these motors is somewhat low\\nfor the use of carbon brushes, the necessity of reversal of\\ndirection and the liability of sparking on over-load make\\ntheir use desirable. Soft carbon brushes of low resistance\\ncan, however, be obtained, and they are to be recom-\\nmended.\\nFig. 160 illustrates a motor which is used on automo-\\nbiles and manufactured by the Eddy Electric Manufacturing\\nCompany. It is a four-pole machine. The frame is ring\\nshape and made of cast steel. The pole pieces, also made\\nof cast steel, are fastened to the frame by bolts and\\nsteady pins. The armature is wound with formed coils\\nwhich are cross connected, and therefore require but two", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0214.jp2"}, "215": {"fulltext": "SERIES MOTORS. 203\\nsets of brushes. These brushes are made accessible by\\nthe existence of a window in the end plate. A pinion\\nwhich is mounted upon the armature shaft meshes with\\nan inside gear placed upon the wheel of the vehicle. A\\nrecess in the exterior of the magnet frame is fitted to re-\\nceive some part of the frame of the vehicle. Clamps for\\nfastening to this frame are provided to suit the character of\\nthe vehicle. The motor is intended to be operated on 75\\nvolts, and is rated at 1.6 horse-power, at the speed of 1400\\nFig. 160.\\nrevolutions per minute. Its weight is 142 lbs., and it\\nhas an efficiency of 79^ per cent at full load. At 100 per\\ncent over-load it has an efficiency of ]6\\\\ per cent, and at\\n150 per cent over-load an efficiency of 73 per cent.\\n106. Mill Motors For many kinds of mill work re-\\nquiring great torque at low speed, reversibility, and wide\\nvariation of speed, the series-wound motor is well adapted.\\nSince mill motors are to be used in places where dust,\\ngrit, and small particles of metal are apt to be floating in\\nthe air, it is necessary, to insure good continuous operation,", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0215.jp2"}, "216": {"fulltext": "204 DYNAMO ELECTRIC MACHINERY.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0216.jp2"}, "217": {"fulltext": "SERIES MOTORS.\\n205\\nm;", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0217.jp2"}, "218": {"fulltext": "206\\nDYNAMO ELECTRIC MACHINERY.\\nthat they be inclosed after the fashion of railway motors.\\nMill motors differ from shunt-wound machines in that they\\nare capable of giving a turning-power, when slowed down\\nor started from rest, many times as great as that given\\nat full speed.\\nFig. 161 shows a Crocker Wheeler mill motor, and Fig.\\n162 shows the same disassembled. It is a bipolar drum\\narmature machine, designed for about 800 R.P.M., and\\ngiving without overheating an intermittent horse-power of\\n14 or a continuous horse-power of 5.\\nIt is rated in this way, since fre-\\nquent stops and starts are expected\\nin the use of such a motor. The\\nhotter a motor gets during an in-\\nterval of use the more it will cool\\noff during an interval of rest. Of\\ncourse an inclosed motor such as\\na mill motor heats up much more\\nrapidly and severely than does an\\nopen motor where the air circulates\\naround the fields and the armature.\\nSince these motors are reversi-\\nble the brushes can have no lead.\\nSparkless running is accomplished\\nby a long air gap. Being series\\nwound the field increases with load\\nand the speed is reduced corre-\\nspondingly, hence commutation is readily effected.\\nThese motors are controlled by a variable series resist-\\nance, the various connections being made in a controller,\\nsuch as is shown in Fig. 163. The circuits are made by con-\\ntact pieces on a cylinder coming in contact with fingers or\\nm%\\\\umm\\nill\\nFig. 163.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0218.jp2"}, "219": {"fulltext": "SERIES MOTORS 2Q J\\nwipers which are mounted on a board forming the back of\\nthe controller. The controller illustrated is also a reverser.\\nThe motor can be run in either direction by moving the\\ncontroller handle to the right or to the left of the central\\nposition.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0219.jp2"}, "220": {"fulltext": "208 DYNAMO ELECTRIC MACHINERY.\\nCHAPTER XL\\nDYNAMOTORS, MOTOR-GENERATORS,\\nAND BOOSTERS.\\n107. Dynamotors. A dynamotor is a transforming\\ndevice combining both motor and generator action in one\\nmagnetic field, with two armatures or with an armature\\nhaving two separate windings. They are generally sup-\\nplied with a commutator at each end, which are connected\\nto the two windings respectively. Either winding of the\\narmature may be used as a motor winding, and the other\\nas the dynamo winding. These machines occupy the same\\nposition as regards direct current practice as is occupied\\nby transformers in alternating current practice. That is,\\nthey enable one to take electrical energy from a system\\nof supply at one voltage, and deliver it at another voltage\\nto a circuit where it is to be utilized. They cannot, how-\\never, be constructed so as to operate with the same high\\nefficiency as a transformer does. As the currents in the\\ntwo armatures flow in opposite directions, and the machines\\nare so designed as to have practically the same number of\\narmature ampere turns when in operation, there is practi-\\ncally no armature reaction. The field, therefore, is not\\ndistorted so as to require a shifting of the brushes, nor is\\nthere sparking present as a result of a change of load.\\nThese machines are more efficient than motor generators,\\nwhich will be described later, as they have but a single", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0220.jp2"}, "221": {"fulltext": "DYNAMOTORS. 209\\nfield. They cannot be compounded so as to yield a con-\\nstant E.M.F. at the dynamo end. A cumulative series\\ncoil would tend to raise the E.M.F. at the dynamo end,\\nbut it would lower the speed of the armature as a motor\\nby a corresponding amount.\\n108. The Bullock Teaser System. Dynamotors are\\nused extensively by the Bullock Electric Manufacturing\\nCompany in their so-called Teaser system of motor-speed\\ncontrol. This system is used in driving large printing-\\npresses from supply circuits, which are at the same time\\nused for lighting and other purposes. Large printing-\\npresses contain very many sets of gears, and possess very\\nlarge moments of inertia. These large machines require\\nan unusually large torque on the part of the motor to start\\nthem. Sometimes it is as much as five or six times that\\ntorque which the motor is called upon to produce at full\\nload. Now, the torque which is exerted by a motor is de-\\npendent upon the current which flows through its arma-\\nture, while the speed at which this torque is applied is\\ndependent upon the impressed electromotive force. As\\nthe current, which is required to produce the normal run-\\nning torque is already of considerable strength, it is desira-\\nble that some direct current electrical transformation be\\nemployed to avoid the excessive starting current. The\\nTeaser system accomplishes this by making use of the\\ndynamotor. The motor winding is designed for five times\\nthe electromotive force of the dynamo winding. Its field\\nwinding is excited directly from the supply mains. The\\nnegative brush of the motor side is connected with the\\npositive brush of the dynamo side. The two armature\\nwindings are connected in series with a regulating resist-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0221.jp2"}, "222": {"fulltext": "2IO\\nDYNAMO ELECTRIC MACHINERY.\\nance to the supply mains. At starting, the main motor,\\nwhich drives the press and which is generally a cumu-\\nlatively compound-wound motor, is supplied with current\\nfrom the dynamo end of the dynamotor. The voltage\\nwith which it is supplied is somewhat less than one-fifth\\nthat of the main supply, depending upon the magnitude\\nof the resistance in series with the dynamotor. This low\\nvoltage permits of the application of a proper amount of\\ntorque at a low speed. Furthermore, the drain of current\\nfrom the supply mains is but about one-fifth that which\\npasses through the main motor. By manipulating the dy-\\nnamo regulating resistance, the electromotive force sup-\\nplied to the main motor is raised, and with it the speed.\\nThe highest speed of the main motor which can be attained\\nby this arrangement is such, that, when attained, the mo-\\ntor s connections may be transferred to the supply mains", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0222.jp2"}, "223": {"fulltext": "DYNAMOTORS.\\n211\\nthrough another series regulating resistance without any-\\nexcessive drain of current from those mains. The arrange-\\nment of the apparatus is shown in Fig. 165, and the\\namount of current which is\\ntaken by the main motor as\\ncompared with the amount\\nof current which is drawn\\nfrom the supply mains is re-\\npresented in Fig. 164. Re-\\ngulation of the resistances\\nand changes of connection\\nare accomplished through the\\naid of a controller. The\\ndifferent speeds are secured\\nby the manipulation of a\\nsingle hand-wheel on the con-\\nFig. 165.\\ntroller, and thus the press-\\nman has at his command a means of manipulating the press\\nwhich is not complicated.\\nVmainmotorV\\n\\\\armature/\\\\\\n109. Dynamotors for Electro-Deposition of Metals. In\\nlarge electro-plating establishments, it is common to in-\\ntroduce a dynamotor, whose two armature circuits are\\nexactly similar, and under ordinary excitation give 5 or 10\\nvolts. The commutators, brushes, collecting devices, and\\nleads are of necessity quite massive. The leads are gener-\\nally so arranged that the two armatures may be placed in\\nseries with each other, or in multiple. The low voltage\\nof platers makes it impracticable to have a machine self-\\nexciting. It is common practice in cities to excite these\\nmachines from no-volt lighting circuits, with a regulating\\nrheostat whose resistance is of such a magnitude as to", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0223.jp2"}, "224": {"fulltext": "212\\nDYNAMO ELECTRIC MACHINERY.\\npermit of the variation of the voltage of the machine over\\na range of 25 per cent of its full-load value. Fig. 166\\nshows a dynamotor constructed by the Eddy Electric\\nManufacturing Company for the electro-deposition of cop-\\nper. Each armature winding gives 10 volts and 4,500\\nFig. Iuo.\\namperes. It is designed to be belt -driven through a large\\npulley at one end of the armature shaft. A small pulley\\nupon the other end is for the purpose of receiving a belt\\nconnected with a small separate exciter. The large split\\nclamps connected with the leads are for the reception of\\nthe terminals of the main conductors.\\nno. The Eddy Company s Rotary Equalizer This is\\na dynamotor having a single field which is excited from a\\n220-volt circuit, and a single armature core upon which is\\nwound two distinct no-volt armatures. One armature", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0224.jp2"}, "225": {"fulltext": "DYNAMOTORS.\\n213\\nhas its commutator on one end of the shaft and the other\\nat the other end. The machine is used in connection with\\na 220-volt generator, to enable one to use it for supplying\\nenergy to a three-wire, no-volt, incandescent lighting sys-\\ntem. The principle of its action can be seen from an\\ninspection of Fig. 167. When the system is unbalanced,\\nFig. 167.\\nthat side which has the smaller load has the lesser drop,\\nand therefore the higher difference of potential. The\\narmature winding of the dynamotor which is connected\\nwith that side acts as a motor, runs the armature, and\\ncauses the other armature winding to act as a generator in\\nraising the pressure of the heavier loaded side. Obvi-\\nously the employment of this system can, in some cases,\\nresult in a considerable saving of copper.\\nin. Other Applications of Dynamotors. The Crocker\\nWheeler Company manufactures a special line of dyna-\\nmotors (Fig. 168) for use in telegraphic work. The motor\\nis designed to be supplied with electrical energy from street\\nservice mains, or from the house-lighting mains in the\\ncase of isolated plants. The generator end furnishes cur-\\nrents at a constant potential, which is different in the case", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0225.jp2"}, "226": {"fulltext": "214\\nDYNAMO ELECTRIC MACHINERY.\\nof different machines. These machines are designed to\\ntake the place of batteries of a large number of gravity\\ncells such as were used, in large quantities, a few years ago.\\nThe cost of operation of a dynamotor for this service is\\nabout one-fifth of what it is in the case of the gravity\\ncells. The space which the machine occupies is but\\nFig. 168.\\n^oV o that of the cells. They are to be preferred to bat-\\nteries also on the ground of cleanliness. Their reliability,\\nwhen supplied by electric energy from large city service\\nmains is equal to that of the cells. The same cannot be\\nsaid in the case of small towns. The telephone companies\\nare also rapidly adopting the dynamotor for the purpose\\nof charging storage cells. With some forms, the charging\\nof the cells can go on continuously, they being at the same", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0226.jp2"}, "227": {"fulltext": "I DYNAMOTORS. 215\\ntime used for telephone purposes. Dynamotors also fur-\\nnish a convenient and satisfactory means of heating\\nsurgeons electro-cauteries. Cautery knives take from 3\\nto 8 amperes at 5 volts, while dome cauteries take from\\n15 to 20 amperes at the same voltage.\\n112. Motor-Generators A motor generator is a trans-\\nforming device consisting of two machines, a motor and\\ngenerator, mechanically connected together. They have\\nthe advantage over dynamotors in that the voltage of the\\nFig. 169.\\ndynamo armature can be made to assume almost any\\nvalue within limits by means of a resistance placed in\\nseries with its field-winding and capable of variation.\\nThey can furthermore, besides being separately excited,\\nbe shunt wound or compound wound. They are used\\nquite extensively in the Ward-Leonard system of motor\\nspeed control, which was described in paragraph 97. They\\nare also used for charging storage batteries. In this case", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0227.jp2"}, "228": {"fulltext": "2l6 DYNAMO ELECTRIC MACHINERY.\\nthey are almost always shunt wound. They are also used\\nin electro-plating establishments. In this case they are\\nseparately excited, as the voltage generally employed in\\nsuch places is too small to give satisfactory self-excitation.\\nFor general laboratory work on tests which require large\\ncurrent at a low voltage or a small current at a high\\nvoltage, motor generators are of inestimable value.\\n113. Boosters. A booster is a machine inserted in series\\nin a circuit to change its voltage, and may be driven either\\nby an electric motor, or otherwise. In the former case it is a\\nmotor-booster. This machine is used very extensively on\\nEdison three-wire incandescent lighting systems which\\nsupply current at a constant potential. Feeders which run\\nto feeding-points at a great distance, if supplied by current\\nfrom the same bus bars as shorter feeders, will have too\\nsmall a difference of potential at the feeding-points to give\\nsatisfactory service. A booster with its field and armature\\nwindings in series inserted in series in the feeder will add\\nE.M.F. to the feeder which in magnitude is proportional to\\nthe current flowing in the feeder, that is, as the current in-\\ncreases the field excitation will increase and with it the\\nE.M.F. produced by the armature. The machine may,\\ntherefore, be so designed as to just compensate for any\\ndrop which is due to the resistance of the feeders and to\\nthe current flowing through them. As all the current of the\\nfeeder must pass through the booster armature, the collect-\\ning devices must be massive and must be designed to carry\\nthese heavy currents. The rating of a booster is of course\\ndetermined by the voltage which it produces, and the total\\ncurrent which passes through it and the feeders. Boosters\\nare also used in the central stations of trolley companies to", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0228.jp2"}, "229": {"fulltext": "DYNAMOTORS. 217\\nraise the voltage which is supplied to the feeders connected\\nwith distant sections of the line. They are also being in-\\ntroduced in office buildings in connection with electric\\nelevator service. When the elevator motors are supplied\\nfrom the same generators as the lights and fans in an office\\nbuilding they give to the generators what is called a lumpy\\nload. The excessive currents demanded by the elevator\\nmotors on starting produce wide fluctuations of voltage in\\nthe mains. A booster inserted in these mains may be\\nmade to add E.M.F. to the mains on these occasions.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0229.jp2"}, "230": {"fulltext": "2l8 DYNAMO ELECTRIC MACHINERY.\\nCHAPTER XII.\\nMANAGEMENT OF MACHINES.\\n114. Connections for Combined Output of Dynamos.\\nIn general a dynamo is much more efficient when operated\\nat its full load than when operated at one-half or one-quarter\\nload. It is usual to install in central stations, which, as a\\nrule, have to supply different quantities of electrical energy\\nat different times of the day, a number of smaller units\\nrather than one unit large enough to supply the total\\nenergy. By this means any load can be handled by a\\nmachine or a number of machines all operating at about their\\nmaximum of efficiency. It is well, therefore, to consider\\nthe methods of combining two or more machines on one\\nload. The simplest and most usual method of connecting\\ndynamos is that employed in incandescent light generating\\nstations. Here a number of constant pressure machines\\nare arranged as in Fig. 1 70, to act in parallel on one pair of\\nbus bars. The figure shows shunt machines with hand\\nregulators. The various external circuits are connected in\\nparallel to the bus bars. This practice is frequently\\nmodified by separating those machines which supply the\\ncircuits that deliver at the more distant points from those\\nthat operate the shorter circuits. This is because the main-\\ntaining of a constant and uniform pressure at all distribut-\\ning points requires a higher pressure on the station ends of\\nthe longer mains than on the shorter. When a machine", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0230.jp2"}, "231": {"fulltext": "MANAGEMENT OF MACHINES.\\n219\\nis to be thrown into circuit on to bus bars already in opera-\\ntion, it is first brought up to speed, the field magnetization\\nis then adjusted till the machine gives the same pressure\\nas exists between the bus bars, and the main switch is then\\nMy\\nMiy\\nmiw rrwMKj\\nFig. 170.\\n-e\\njf0-\\nW\\nclosed, which puts the machine in circuit. The proper\\npressure at which to throw in the new machine may be\\nroughly determined by comparing the relative brightness\\nof its pilot lamp with that of the lamps operating on the\\ncircuit.\\nA more exact way is to\\ncompare the readings of a\\nvolt-meter across the ter-\\nminals of the machine with\\none across the bus bars.\\nThe most convenient way is\\nto use a cutting-in galvano-\\nmeter. Of these there are\\ntwo forms, the zero galvanometer and the differential gal-\\nvanometer. The zero galvanometer, shown with connec-\\ntions in Fig. 171, has a single coil of high resistance.\\nWhen the pressure of the machine is not exactly that of\\nthe bus bars a current will flow one way or the other, and\\nr jmw\\nFig. 171.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0231.jp2"}, "232": {"fulltext": "220\\nDYNAMO ELECTRIC MACHINERY.\\nt\\nBUS\\nthe needle will be correspondingly deflected. When there\\nis no deflection, the machine may be thrown into circuit.\\nThis instrument is simple and cheap, but it requires that\\none terminal of the machine be permanently connected to\\na bus, which is not always desirable. The differential gal-\\nvanometer, Fig. 172, has two high resistance coils, one in\\nshunt across the bus bars, and one in shunt across the\\nmachine terminals.\\nWhen equal pressures are\\nimpressed on each of the\\ncoils, they, by their differ-\\nential action, hold the needle\\nin equilibrium, but when one\\ncoil is subject to more pres-\\nsure than the other a deflec-\\ntion occurs. This instrument\\nis more costly and more\\ncomplex than the last, but it has the advantage that a two-\\npole switch may be used to cut in or out the machine.\\nWhen shunt machines are connected in parallel, it is\\nexpected that they will all be kept at the same pressure.\\nIf they are not, no serious damage is likely to occur, since\\nthe lower pressure machine merely fails to take its full\\nshare of the load. If the pressure of one machine falls so\\nlow that it is overpowered and run as a motor, still no\\ndamage will result, save perhaps the blowing of a fuse,\\nsince the direction of rotation for a shunt machine is the\\nsame whether it be run as a dynamo or as a motor. If it\\nbe desired to regulate a number of machines together by\\none regulator, it may be accomplished by bringing the\\npositive ends of the field coils to one side of the regulator\\nand connecting the other side to the negative bus.\\nFig. 172.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0232.jp2"}, "233": {"fulltext": "MANAGEMENT OF MACHINES.\\n221\\nShunt machines may be operated in series by connecting\\nthe positive brush of one machine to the negative brush of\\nthe next, and connecting the extreme outside brushes with\\nthe line wires. When this is done each machine can be\\nregulated separately to generate any portion of the pressure.\\nIf it be desired to regulate all the machines thus connected\\nuniformly and as a unit, the field coils of all the machines\\nmay be put in series with one regulating rheostat, and\\nshunted across the extreme brushes of the set. In the\\nEdison three-wire system two 115-volt direct-connected\\nshunt machines are mounted on one engine shaft. The\\ndynamos are connected in series as described above, the\\nneutral wire being connected to the united brushes, as in\\nFig. 173.\\nSeries-wound dynamos may be operated in series with-\\nout any difficulty, though it is not customary to do so.\\nSeries generators are used almost exclusively on constant\\ncurrent (arc light) circuits, and it is usual to have as many\\nmachines as there are external circuits, each machine being\\nof capacity enough to operate that circuit alone. A new\\nform of Brush generator supplies\\nseveral series circuits from its\\nterminals, and regulates for all\\nof them. If it be attempted to\\noperate series dynamos in paral-\\nlel, the following difficulty occurs\\nIf the machines start with a\\nproper distribution of load among\\nthem and one does not generate\\njust its full pressure, then this one does not continue to take\\nits full share of the load and, since it is series wound,\\na decrease in load is followed by a decrease in pressure.\\n^-a\\nFig. 173.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0233.jp2"}, "234": {"fulltext": "222\\nDYNAMO ELECTRIC MACHINERY.\\nThe conditions become always more uneven until the\\nmachine is overpowered and it turns into a motor. Since\\nthe direction of rotation of a series-wound motor is oppo-\\nsite to its direction when run as a dynamo, serious results\\nmay occur. The only remedy for this trouble is to arrange\\nthe field coils so that the magnetization in any one machine\\nwill remain the same as in the other machines, even though\\nits pressure falls below that of the others. To accomplish\\nthis the series fields must all be placed in parallel. This\\nmay be done by means of an equalizer, which is a wire of\\nsmall resistance connected across one set of brushes, and\\nby placing the fields in parallel, as shown in Fig. 1 74. Two\\nFig. 174.\\nseries dynamos may be run in parallel without an equalizer\\nby resorting to mutual excitation, that is, by letting the cur-\\nrent of one armature excite the field of the other. In this\\ncase if the pressure of one machine falls and its load there-\\nfore decreases, the magnetization of the other is reduced,\\ncompelling the first to maintain its share of the load.\\nSeries dynamos are never operated in parallel in practice,\\nbut this discussion is introduced because of its application\\nto compound-wound dynamos.\\nThe use of compound generators for constant pressure\\ncircuits is very common. Since these have series coils\\nthey cannot be run in parallel without special arrange.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0234.jp2"}, "235": {"fulltext": "MANAGEMENT OF MACHINES.\\n223\\nments. It is usual to fit the series coils with an equalizer,\\nas in Fig. 175. The desired end might be accomplished\\nin the case of two ma-\\nchines by making the J\\nseries coils mutually ex-\\nciting.\\n4\\nSHUNT\\nmm.\\nUffl\\nERIE?\\nMl\\n\u00e2\u0096\u00a0O\\nFIELD COILS\\nsma\\nm.\\nFig. 175.\\n115. Connections of\\nMotors for Combined\\nOutput. Any number\\nof shunt motors may be placed in parallel across mains\\nof a constant pressure, and their operation will be sat-\\nisfactory whether each has a separate load or whether\\nthey be connected through proper ratios to one shaft.\\nShunt motors will operate in series on a constant pressure\\ncircuit when positively connected together but if con-\\nnected to the same shaft by belts, and one belt slips or\\ncomes off, that motor will race, and rob its mates of their\\nproper portion of the voltage. This arrangement is not\\ncommon.\\nSeries motors will operate satisfactorily on constant\\npressure circuits but when two or more such machines,\\nthat are arranged in parallel on a constant pressure circuit,\\nare connected to one shaft an equalizing connection is\\nsometimes used. Series motors in series on constant\\npressure mains will operate satisfactorily, dividing up the\\ntotal voltage between them according to the load each is\\ncarrying. If it be desired to make them share a load\\nequally they must be geared together so that each rotates\\nat the speed corresponding to its share of the voltage.\\nSeries motors only are used on constant current circuits.\\nAny number of these may be placed in series on such a", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0235.jp2"}, "236": {"fulltext": "224 DYNAMO ELECTRIC MACHINERY.\\ncircuit individually or connected to a common shaft. A\\nseries motor on a constant current circuit may be over-\\nloaded until it stops without harm, since a constant current\\nflows at any speed.\\nCompound-wound motors are coming into quite, general\\nuse, and they are invariably operated on constant pressure\\ncircuits, and each machine has its own load.\\nIn ordinary electric railroad practice, as has been stated,\\nthere are two series-wound motors to a car, operating\\neither in series or parallel, according to the position of the\\ncontroller handle, on a constant pressure of 500 volts.\\nEach of these motors is geared to a separate pair of driv-\\ning-wheels. Since under ordinary conditions the rate of\\nrotation of the two motors is the same, the E.M.F. sup-\\nplied to each is the same when they are in series, and\\nsince the current is common they divide the work evenly.\\nWhen in parallel the pressure on each is 500 volts, and\\nsince the rotations are the same the currents will be the\\nsame and the load will be divided evenly. It often occurs\\nthat the back platform of a car is so loaded that the front\\ndrivers slip when the power is applied at starting. This\\noccurs when the motors are in series and the current\\nis common to the two. But the higher rate of rotation of\\nthe front motor causes it to generate a greater counter\\nE.M.F. thus lowering the pressure acting on the rear\\nmotor. Thus more electric energy is consumed in the\\nfront motor, and the surplus of work turns into heat from\\nthe friction between the slipping wheels and rails. When\\nthe car gains such a velocity that the front wheels bite the\\nrails, the work is again evenly distributed between the two\\nmotors. It should be remembered that this occurs only\\nwhen the motors are in series.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0236.jp2"}, "237": {"fulltext": "MANAGEMENT OF MACHINES. 225\\n116. Care and Operation of Machines In what follows\\non the operation of motors and dynamos, it is assumed\\nthat the machine is properly designed and of sufficient\\ncapacity for the work it is called upon to perform. For\\nsatisfactory operation, the machine must be connected with\\nan appropriate circuit and one of the voltage or amperage\\nfor which the machine was designed. Further it is\\nassumed that the mere mechanical details have been looked\\nto, such as proper foundation, proper alignment with shaft-\\ning, and good lubrication. Only electrical trouble will be\\ntreated.\\nIf trouble be detected, a machine should be at once\\nstopped to prevent further trouble. In central generating\\nstations, one of the most positive rules is not to shut\\ndown while any possible means is left to keep running.\\nIn such plants there are always one or two units held in\\nreserve, and one of these may be started and substituted\\nfor a machine developing a fault so that the latter may be\\nshut down and its fault remedied.\\nSparking at the brushes is the most general trouble, and\\nit has more causes than any other. The brushes must\\nmake good contact with the commutator, they must be\\ntrue, and have good contact surface. The commutator\\nmust be clean. Any collection of carbonized oil is sure to\\ncause sparking. A very thin layer of good oil, free from\\ndust, is advantageous. On a bipolar machine the brushes\\nmust be diametrically opposite, on a four pole exactly 90\\napart, etc. This condition must be attained while the\\nmachine is at rest, either by actual measurement or by\\ncounting the commutator bars between each brush. If\\nthe brushes of one set are staggered they may cover\\ntoo much armature circumference and cause sparking.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0237.jp2"}, "238": {"fulltext": "226 DYNAMO ELECTRIC MACHINERY.\\nThe brushes must be set at the proper point. This is\\naccomplished while the machine is in operation under its\\nrequired load. The rocker arm, which carries all the\\nbrush holders, is moved carefully back and forth until the\\npoint of minimum sparking is found. Sometimes there is\\nquite an arc of movement in which sparking is not\\nobserved. The brushes should then be set at the center\\nof this arc, since heating occurs when the brushes are off\\nthe proper commutating point, even if sparks be not seen.\\nSparking may be due to fault in the commutator. A\\nhigh-bar, a low-bar, or fiat, projecting mica, rough or\\ngrooved surface, eccentricity, or any condition of surface\\nwhich causes the brushes to vibrate and lose contact with\\nthe commutator will surely cause sparking. If sparking\\nbe allowed to go without correction, it will pit the commu-\\ntator and aggravate these conditions. If the irregularity\\nof surface be slight, it may be cut down by sandpaper\\n(never emery) held in a block cut to fit the commutator.\\nIf the surface be very bad, it must be cut down by a\\nmachine. A small armature may be swung in a lathe but\\na large one must be left in its own bearings, and a tool\\nheld against the commutator by some special device. A\\nperfectly true commutator may act eccentrically toward\\nthe brushes because of wear in the shaft bearings. New\\nbearings will remedy this fault.\\nIf a coil of the armature be short-circuited, periodic\\nsparking may result. The coil is liable to burn out if the\\nmachine is not immediately stopped. The short circuit\\nmay occur from breakdown of the insulation within the\\narmature, in which case rewinding is necessary or it may\\nbe caused by metal chips or the like at or near the com-\\nmutator, in which case the cause can be easily removed.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0238.jp2"}, "239": {"fulltext": "MANAGEMENT OF MACHINES. 227\\nWhen a coil is broken very violent sparking occurs, since\\nhalf the armature current is broken every time the com-\\nmutator bar connected to the broken coil passes from under\\na brush. Such a break may occur within the armature,\\nrequiring rewinding but it is more likely to occur where\\nthe coil end is attached to the commutator bar lug. If\\nthe break be at this place, the wire needs but to be screwed\\nor soldered to the lug and the machine is repaired.\\nIf the field of a motor is too weak, sufficient counter\\nE.M.F. is not generated, and excessive current flows and\\ncauses sparking. The weakening of the fields may occur\\nfrom a short circuit in the field coils or two or more\\ngrounds between the field coils and the pole piece, or by a\\nbroken field circuit (shunt coils) which reduces the mag-\\nnetism to almost zero. In any case, unless the trouble is\\nto be found external to the coils, rewinding is necessary.\\nHeating of machines is another frequent source of\\ntrouble. The limit of temperature that may be allowed in\\nthe bearings depends on the flashing-point of the lubricant\\nused, but a well designed and lubricated bearing ought\\nalways to run cooler than the commutator or armature.\\nThe limit of temperature that may be allowed in the arma-\\nture depends on the baking -point of insulation used,\\nand also on the melting-point of the solder used if the\\ncoil ends are soldered to the commutator lugs. A good\\ngeneral rule is this If you can hold your hand on any\\npart of the machine for more than a few seconds, that\\npart is not dangerously hot. Of course metal feels warmer\\nthan insulating cotton for the same temperature, and\\nallowance should be made for this. If a burning smell or\\nsmoke comes from a machine, the safe temperature limit\\nhas been far exceeded, and the machine should be shut", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0239.jp2"}, "240": {"fulltext": "228 DYNAMO ELECTRIC MACHINERY.\\ndown at once. This indicates a serious trouble a short\\ncircut or a hot bearing probably.\\nIf the trouble arises from the bearings the ordinary me-\\nchanical precautions of cleaning, aligning, lubricating, etc.,\\nwill generally cure it. Never use water to cool hot bearings.\\nIf water gets into the windings of either the field or the\\narmature, short circuits will occur and ruin the machine.\\nIt must not be assumed that because one part of a\\nmachine is hot the trouble lies with that part. Heat is\\nquickly conducted all over a machine and when heat is\\ndetected in one place the machine should be felt all over,\\nthe hottest part probably being the part at fault. The\\nbrushes of a machine should not be set too tight, for, be-\\nsides reducing the efficiency greatly, they cause much\\nheat from friction. The commutator should not be more\\nthan 5\u00c2\u00b0 C. hotter than the armature.\\nMachines that operate on constant pressure circuits are\\nliable to overheat because of too much current flowing\\nthrough some parts of them. This may result from over-\\nloads, in which case the remedy is obvious, or because of\\nshort circuits in the machines, in which case rewinding is\\ngenerally necessary. In the case of constant potential\\ngenerators a short circuit of the mains will produce a sud-\\nden and severe overload, which can only be remedied by\\ntracing out the lines and removing the short circuit.\\nWhen a machine makes an unwarranted amount of noise\\nit usually indicates the need of attention. Carbon brushes\\nchatter and spark sometimes when the commutator is\\nsticky, the action being something like a bow on a violin\\nstring. Cleaning the commutator will cure this. Hum-\\nming and vibration result when the revolving parts are\\nnot revolved about their center of gravity. This may be", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0240.jp2"}, "241": {"fulltext": "MANAGEMENT OF MACHINES. 229\\nbecause of faulty construction or warping after completion.\\nIf the fault be with the pulley, it may be turned out or\\ncounterweighted. If the shaft be sprung it may be\\nstraightened or a new one used. If the armature core or\\nwindings be out of balance, there is not much help for it.\\nSlower speed will reduce the noise from this cause.\\nNoise may occur from the armature rubbing or striking\\nagainst the pole faces. This is a serious matter, and if not\\nimmediately attended to results in the destruction of the\\narmature. It is caused generally by wear in the shaft\\nbearings, in which case new brasses will remedy the\\ntrouble. Sometimes it results from a sprung shaft, in\\nwhich case the shaft must be either straightened or re-\\nplaced. A rattle produced by loose collars, bolts, nuts, or\\nconnections would indicate that these parts needed setting\\nup or adjusting.\\nIf a motor revolves too slowly, it may be because of an\\noverload of mechanical work, because of excessive friction\\nin the machine, or because of the armature rubbing against\\nthe pole face. A variation in the pressure supplied to a\\nmotor causes a variation in speed. If the field magnetism\\nbe too weak the motor will revolve too fast when not\\nloaded, and too slow when under full load, and will take\\nexcessive current. A weak field may be caused by a short\\ncircuit which cuts out some or all of the field turns, or by\\na broken field circuit. If the load be removed from a\\nseries motor on a constant current circuit it will race badly\\nunless its field coils are shunted. Practically such a motor\\nshould not be used in any position where it may be sud-\\ndenly relieved of its load, as by the slipping of a belt. A\\nshunt motor, whose fields are not excited, will run either\\nforward or backward when a current is allowed to flow in", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0241.jp2"}, "242": {"fulltext": "230 DYNAMO ELECTRIC MACHINERY.\\nthe armature, according to the relative magnitudes and\\ndirections of the residual magnetism and the armature re-\\nactions. Ordinarily, however, if a motor runs backward, it\\nmay be assumed that the connections are wrong. Usu-\\nally changing the connections to the brush holders, so that\\nthe brushes change their signs without changing any other\\nconnections, will make the motor change its direction of\\nrotation. A series motor also may be made to change its\\ndirection by changing the direction of current flow in\\neither field coils or armature, but. not in both.\\nOn starting up, a self-exciting dynamo is supposed to\\nbuild up its voltage to normal, having at first no excitation\\nsave that of residual magnetism. After standing some\\ntime, or in proximity to other dynamos, or after being\\nhammered, the magnet frame may have lost all its residual\\nmagnetism. In this case the machine does not build up\\nwhen revolved. By passing a current from another\\nmachine through the field coils the dynamo will generate\\nas a separately excited one. Then the exciting current\\nmay be thrown off and the self-excitation thrown on, when\\nthe machine will build up satisfactorily. If the residual\\nmagnetism becomes changed in direction, or the separately\\nexciting current be passed in the wrong direction, then\\nwhat little voltage may be generated will, when connected\\nfor self-excitation, send the current in such a direction as\\nto tend to demagnetize the field, and building up will be\\nimpossible. A shunt machine builds up better the less\\nthe outside load, since at no load the terminal voltage is the\\ngreatest and the most likely to send a magnetizing current\\nin the field coils. A series machine builds up better when\\nthe outside load is increased. Such a machine may even\\nbe momentarily short circuited to make it build up. For a", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0242.jp2"}, "243": {"fulltext": "MANAGEMENT OF MACHINES. 231\\ngiven voltage resulting from residual magnetism, the current\\nin the field coils is greater the less the resistance in the\\ncircuit. If the connections to one of the field coils in a\\nbipolar machine be reversed, causing two poles of the same\\npolarity, the machine will of course fail to generate. This\\ncondition may be detected by the use of a compass needle.\\nSmall machines sometimes generate at starting a few volts,\\nshowing proper connections and the presence of some\\nresidual magnetism, but refuse to build up beyond this\\npoint. It is sometimes convenient to materially increase\\nthe speed of such a machine, whereupon it will build up\\nrapidly, and the speed may then be reduced to normal, and\\nthe dynamo will continue to generate at its normal pres-\\nsure.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0243.jp2"}, "244": {"fulltext": "232 DYNAMO ELECTRIC MACHINERY.\\nCHAPTER XIII.\\nTHE DESIGN OF MACHINES.\\n117. Different Methods of Design. It is impossible to\\nlay down a fixed set of rules to be followed in the design\\nof dynamo electrical machinery. This is because the\\nspecified conditions of operation and construction are\\nseldom alike in two cases. A designing engineer may be\\ncalled upon to design a machine of a given output at a given\\nvoltage, the field frame, however, to be chosen from one of a\\nset already in stock and again it may be required that the\\nmachine shall be direct connected, the output, the voltage,\\nand the speed of rotation being given still, again, the\\ncapacity, the maximum gross weight, and the efficiencies of\\noperation at various loads, may be specified, as in the case\\nof an automobile motor or he may be called upon to design\\na machine of a given output and voltage, which shall\\noperate at a satisfactory efficiency, and which shall have a\\nfirst cost which will enable the manufacturer to successfully\\ncompete with others in the sale of his products. Through-\\nout the calculations the engineer is obliged to refer to his\\nexperience or the experience of others in determining the\\nvalues of different quantities which must be assumed before\\nthere can be any further progress on the design. Further-\\nmore, after having assumed certain values, results which\\nare arrived at later on in the work will necessitate the re-\\njection of these values and the assumption of new ones.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0244.jp2"}, "245": {"fulltext": "THE DESIGN OF MACHINES. 233\\nOftentimes what one might desire as a value for one quan-\\ntity is undesirable, because it conflicts with the adoption of\\na value for some other quantity which is more desirable. In\\nthe following paragraphs a method is given for designing\\na machine under the conditions specified.\\n118. Specifications. The following specifications are\\ngiven and must be complied with\\nThe type of machine as regards the shape of its field\\nframe, its bearings, and the method of its being driven its\\noutput in kilowatts its terminal voltage at full load and at\\nno load the materials from which are to be constructed its\\nfield frame, its pole pieces, its armature core, its brushes,\\nits shaft, its bearings, its armature spider, and its con-\\nductors and the insulation throughout its various parts.\\n119. Preliminary Assumptions. The design will be\\nbased upon an assumption of the values of four different\\nquantities.\\nThe first assumption is that of the value of the flux den-\\nsity in the air gap, which will be represented by g The\\nvalue which will be chosen will depend somewhat upon the\\nmethod to be employed for obviating armature reaction.\\nAlmost all designers rely upon a stiff, bristly field to assist\\nin preventing a distortion of the field when under load, and\\ntherefore higher flux densities are being used now than\\nwere a few years ago. Higher densities are used when the\\npole pieces are made of wrought iron or of cast steel than\\nwhen they are made of cast iron. The densities are greater\\nin the case of multipolar machines than in the case of\\nbipolar and they increase, within limits, with the size of\\nthe machine. A value between 4000 and 7500 should be\\nchosen.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0245.jp2"}, "246": {"fulltext": "234 DYNAMO ELECTRIC MACHTNERY.\\nThe second assumption is a value for the peripheral\\nvelocity V of the armature in feet per minute. The com-\\nmon assumption in the case of drum armatures for all sizes\\nabove five k.w. is 3000 feet per minute. High-speed ring\\narmatures have a higher value, ranging between 4000 and\\n6000. The larger value is to be used in the case of large\\nmachines.\\nThe third assumption is a value for the current density\\nin the armature conductor at full load. Inspection of a\\nlarge number of machines shows the use in many of them\\nof from 500 to 800 circular mils per ampere. Sometimes\\nas small a cross-section as 200, and in other cases as large\\nas 1 200 circular mils per ampere, have been found. The\\nlow value is used in the case of machines subjected to\\nperiodic loads of short duration. This is the case with\\nelevator motors, pump motors, sewing-machine motors,\\ndental drill motors, and motors on special machinery. The\\nhigh value is used on machines to be used in central stations\\nfor lighting or power purposes. The specified output in\\nkilowatts divided, by the full-load terminal volts gives the\\ntotal current output of the machine at full load. This,\\ndivided by the number of armature circuits, gives the cur-\\nrent which must be carried by each conductor at full load.\\nThis current multiplied by the assumed value of the number\\nof circular mils per ampere gives the cross-section of the\\nconductor in circular mils. Oftentimes a single armature\\nconductor is made up of several wires in multiple. The\\nmultiplicity of wires affords pliability in winding, and\\nobviates, to a certain extent, eddy currents. Again, the use\\nof copper bars for windings is common, they being in-\\nsulated by the use of micanite, fuller board, or other\\nsheet insulating materials. A cross-section sketch of a", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0246.jp2"}, "247": {"fulltext": "THE DESIGN OF MACHINES. 235\\nsingle conductor should be made in which the dimensions\\nare given of the copper and of the insulating material.\\nThe fourth assumption is the value s to be given to the\\npolar span, s represents the percentage of the armature\\ncircumference which is covered by the faces of the poles.\\nThis value varies considerably within narrow limits, but\\nunless there is some special reason for the assumption of\\nanother value 0.8 may be taken.\\n120. Design of the Armature 1. To determine the\\nspecific induced E.M.F. in volts per foot of active con-\\nductor.\\nV 30.5\\n60 g 10 8\\nE X s g X 30.5 8 volts.\\nwhere the first term in the right-hand member represents\\nthe velocity of the moving conductor in centimeters per\\nsecond, the second term represents the average induction\\ndensity of the flux which enters the armature, and the\\nthird term consists of constants to reduce feet to centi-\\nmeters, and c. g. s. units to volts.\\nII. To obtain the length of active conductor I 1 in feet.\\nl r 7 X number of armature circuits.\\nE\\nIII. To obtain the number of active conductors S upon\\nthe armature.\\nLet ly the number of layers in the armature winding.\\np the assumed ratio of the length to the diameter of the\\narmature core.\\nd the mean winding diameter of the armature in inches.\\nw the specific peripheral width of one armature conductor\\nin inches. (In the case of a smooth-core armature\\nw represents the width of the armature conductor", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0247.jp2"}, "248": {"fulltext": "236 DYNAMO ELECTRIC MACHINERY.\\nplus the double thickness of its insulation, both in\\ninches, while in the case of tooth armatures w rep-\\nresents the width of one tooth plus the width of\\none slot divided by the number of conductors in\\none slot in one layer.)\\nThe length of the armature core pd inches ft.\\n12\\nand the circumference of the core -n-d inches. The\\nivd\\nw\\ndly\\nnumber of armature conductors in one layer hence\\nw\\nthe total number of armature conductors .S 7n\\nSince\\n_, _ ird pd\\nly\u00e2\u0080\u0094 X\\nw 12\\nV iclvt\\n2\\nrlyp\\nirlyd irly ll w 1 2 _ /7T 2 /y 2 wi2\\nw w /v V ivlyp V uPlyirp\\ni\\nI2 7r/j\\nwp\\n,7\\nIn practice the width of the tooth ranges from 50 per\\ncent to 80 per cent, the width of the slot. In some cases\\nit has a width equal to that of the slot. The value for 5\\nyielded by this formula must, in nearly all cases, be altered\\nby either the addition or subtraction of a few conductors\\nin order to make it possible to employ the type of winding\\nwhich it seems desirable to adopt. The change may neces-\\nsitate a slight alteration of one of the assumed values, and\\nas a result the values derived from it.\\nFor machines whose speed is prescribed, as is the case\\nwith direct connected machines, one may use the form of", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0248.jp2"}, "249": {"fulltext": "THE DESIGN OF MACHINES. 237\\nthe formula 5 where d is to be obtained as de-\\nw\\nscribed in the end of the next paragraph.\\nIV. To obtain the diameter of the armature d in inches.\\nSw\\nd inches.\\n7T\\nIn case the speed of the armature in revolutions per\\nminute Fbe prescribed, as is the case with direct connected\\nmachines, the preliminary assumption of the peripheral\\nvelocity V f immediately gives a value for the armature\\ndiameter. y yl\\nd -=zr ft. inches.\\nV. To determine the length of the armature I in inches.\\nI dp.\\nVI. To determine the internal diameter of the armature\\ncore d in inches. In determining this quantity a value for\\nthe flux density in the armature core (E a must be assumed.\\nWiener states that in incandescent dynamos, in railway\\ngenerators, in machines for power transmission and distri-\\nbution, and in stationary and railway motors, the density\\nvaries from 5,500 to 15,500. Ring armatures have higher\\ndensities than drum armatures, low-speed machines higher\\ndensities than high-speed machines, and bipolar machines\\nhave larger densities than multipolars. (B a 8000 is a\\ngood assumption.\\nIf the machine have pairs of poles, the flux which\\nenters the armature through one pole\\n/tt//(V(2.54) 2\\na Jp", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0249.jp2"}, "250": {"fulltext": "238 DYNAMO ELECTRIC MACHINERY.\\nthat is, the surface of the armature in square centimeters\\ntimes the average gap density divided by the number of\\npoles. Considering that but 75 per cent to 80 per cent of\\nthe length of the armature core is made up of iron, the\\nrest being due to the spaces between the laminations and\\nthe width of the ventilating ducts, the radial depth of the\\narmature core is\\nd- d\\nd r d\\n^a/0.75 (2.54)2\\n4 a\\n(B a /o. 75 (2-S4) 2\\nVII. To determine the armature losses. The armature\\nas already determined would theoretically operate satis-\\nfactorily, but there is a possibility of its heating excessively\\nwhen running under full load. There are the two constant\\nsupplies of heat, namely, that due to ohmic resistance\\nand that due to hysteresis and eddy currents. There are\\nalso two avenues for the escape of heat, namely, radia-\\ntion and air convection. An equilibrium is established when\\nthat temperature is reached which will make the escaping\\nheat per unit of time equal to the amount of heat gen-\\nerated in the same time. Concerning the escape of heat\\nby radiation, it should be borne in mind that the watts\\nradiated vary as the difference in temperature between the\\nradiating body and the surrounding atmosphere and as the\\nemissivity and the area of the radiating surface. There\\nis also on starting a conduction of heat to neighboring\\nbodies. After a short time, however, a static temperature\\ncondition will be established. The power loss in hysteresis\\nin the armature is\\n1 V\\nP h -qp (V 6 ^r- V WattS,\\nIO DO", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0250.jp2"}, "251": {"fulltext": "THE DESIGN OF MACHINES. 239\\nwhere 77 equals the hysteretic constant of the iron (0.002), v\\nequals the volume of the armature core in cubic centimeters.\\nThe assumption is made that the flux density in the arma-\\nture core is uniform. This is not true for the main core, as\\nwas shown by Goldsborough, and in the teeth the density is\\nmuch greater. When the volume of the latter is a relatively\\nlarge amount of the total core volume, a correction should\\nbe made. When making many designs, in which the same\\nquality of iron is to be used, it is much easier to get the\\nhysteresis loss per cubic inch at various densities from\\ntables made up to suit the iron. The power loss due to\\nohmic resistance\\np __ ^max 2J\u00c2\u00a3\\nr \\\\number of armature circuits/ a\\nwhere I max is the full-load current of the machine in am-\\nperes, and R a is the resistance of all the armature con-\\nductors arranged in series. Before getting P h and P r one\\nmust determine the values in VIII. to XL\\nVIII. To obtain the armature speed V in revolutions per\\nmintite. This quantity is prescribed in the case of direct\\nconnected machines. In other cases in may be determined\\nby the formula\\nird\\nIX. To obtain the volume of the armature core v in cubic\\ncentimeters.\\nv zlirl 1 (2.54) 3\\nwhere z is a coefficient which represents that part of the\\narmature core length which is occupied by iron. In ordi-\\nnary laminations the space occupied by air and insulating", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0251.jp2"}, "252": {"fulltext": "240 DYNAMO ELECTRIC MACHINERY.\\noxide on the plates amounts to 10 per cent, therefore under\\nthese circumstances z 0.9. The introduction of ventilat-\\ning ducts reduces this value by an amount which can be\\nreadily determined.\\nX. To obtain the resistance of the armature wire in\\nohms. The total length of the armature wire,\\nwhere k is a constant greater than unity, which takes into\\naccount the amount of dead wire employed in making the\\nend connections. This value depends upon the value of\\np and upon the method of winding. In the case of formed\\ncoils its value may be determined from measurements upon\\na single coil. This value is generally slightly greater\\nthan 2. Considering that the resistance of a hot mil foot is\\n1 1.5 ohms, the resistance of the armature\\n1 1.5 I k\\nR n\\ncross-section in circular mils.\\nXI. To obtain the area of the armature radiating sutface\\nA in square inches,\\nA 7T Id\\n(d 2 d 2\\nXII. As 2 to 2\\\\ watts can be radiated per square inch\\nof armature surface without excessive heating, the value of\\ndetermines whether the armature is properly de-\\nA\\nsigned or not. If the fraction is less than 2, the armature\\nis needlessly large, and should be redesigned. If the frac-\\ntion is greater than 21, the armature will heat excessively,\\nand should also be redesigned.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0252.jp2"}, "253": {"fulltext": "THE DESIGN OF MACHINES. 241\\n121. Design of the Field. XIII. Dimensions of the\\npoles and field frame. The design of a field requires judg-\\nment and experience on the part of the designing engineer,\\nand an acquaintance with the various machines of the type\\nbeing designed. One must assume values for the following\\nquantities the flux density in the poles (B^, the flux\\ndensity in the magnet frame B yi the coefficient of magnetic\\nleakage A, and the ratio of the length of a pole to its diam-\\neter in case it has a circular cross-section, or to some other\\ndimension in case it is not circular. The assumption is\\nmade here that the field frame is of a circular type, and\\nthat the pole is of circular cross-section. It is customary\\nto choose such a value for (E yJ that the magnetization will\\nbe carried over the knee of the magnetization curve. In\\nthe case of (By, however, it is customary to choose a value\\nsomewhat below the knee. The coefficient of magnetic\\nleakage for this type of machine is 1.4. A careful design\\nreally requires a knowledge of the distribution of the leak-\\nage flux. Long experience enables one to make allow-\\nance for this. From these assumed values one gets a\\nvalue for the cross-section of a pole,\\nA p sq. centimeters,\\nwhence it follows that the diameter of the pole in inches\\nd p 2.54 V/ inches, and the cross-section of the frame,\\nA f sq. centimeters.\\n2 Q6 f\\nXIV. Reluctance of the magnetic circuit. After mak-\\ning a provisional scale-drawing of the field-magnet frame\\nwith its poles and the armature core, exercising judgment\\nderived from experience or from the inspection of other", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0253.jp2"}, "254": {"fulltext": "242\\nDYNAMO ELECTRIC MACHINERY.\\ndrawings, determine the average length in centimeters of\\nthe path of the magnetic lines in the frame, in the poles,\\nin the air gap, in the teeth, and in the armature core.\\nFig. 176.\\nRepresent by l fy l p l gi l t and l t the length in centimeters\\nof the parts marked in Fig. 176. From the assumed\\nvalues of the flux density, and from the magnetization\\ncurves of the metals from which the various parts of the\\nmagnetic circuit are constructed, one can get the respec-\\ntive permeabilities. The reluctance may then be calculated\\nas follows\\n7\\nReluctance of the pole (R p\\nH A j\\nI*\\nof section of field frame Gi f\\nfx f A f\\n7\\nof the air gap 6i g\\nof section of the armature core,\\np a zl{d-d )(2. S tf", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0254.jp2"}, "255": {"fulltext": "THE DESIGN OF MACHINES.\\n243\\nTo determine the reluctance offered by the teeth and\\nwinding-slots, it is convenient to assume that the total flux\\nis carried by the teeth alone. Owing to the fringing of\\nthe field at the pole tips, not merely the teeth immediately\\nunder the pole face carry the flux from that pole, but, with\\nvery short air gaps, an extra tooth takes part in the trans-\\nTABLE OF TOOTH-DENSITY CORRECTIONS.\\nCorrected Iron\\nDensity.\\nDensities on the\\nAssumption that the Iron Transmits\\nthe Entire Flux.\\nLines per Sq. Cen-\\ntimeter.\\nTooth Width m\\nSlot Width.\\nTooth Width\\nf Slot Width.\\nTooth Width r=\\nSlot Width.\\n17050\\n18000\\n19050\\n20000\\n21020\\n22000\\n23100\\n17200\\n18450\\n19680\\n21050\\n22200\\n24000\\n26000\\n17380\\n18600\\n20000\\n21300\\n23000\\n24800\\n26800\\n17510\\n18800\\n20200\\n21850\\n23700\\n2 5500\\n28400\\nTOOTH DENSITY CORRECTION CURVES\\nT WI\\nS =WI\\nDTH OF\\n3TH OF\\nTOOTH\\nSLOT\\n4r\u00c2\u00ab\\n-V*\\nA\\nk\\ny\\n19 20 21 22 23 24 25 2fi\\nUNCORRECTED DENSITY KILOLINES PER SQ, CM.\\n28\\nFig. 177.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0255.jp2"}, "256": {"fulltext": "244\\nDYNAMO ELECTRIC MACHINERY.\\nmission. With large air gaps two or three extra teeth may-\\ntake part. The value of the permeability obtained from\\nthe flux density which is calculated upon the above as-\\nsumption would be too small. The value of the reluc-\\ntance based upon it would in consequence be too large.\\nThe flux density arrived at will have to be corrected by\\nreference to the table on page 243.\\nThe permeability, /x t corresponding to the corrected dens-\\n23000-\\nI\\n22000\\n21000\\n20000\\n19000\\nf\\n4\\n1\\n18000\\ns\\n17000\\n100 200 300 100 500 600 700 800 900 1000 1100 1200 1300 1100 1500 1600 JC\\n10 20 30 10 50 60 70 80 90 100 110 120 130 110 150 160 \\\\l\\nFig. 178.\\nityand to be obtained from Fig. 178, should be inserted in\\nthe formula for the reluctance of the teeth,\\nh\\nR*-=\\nPtA", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0256.jp2"}, "257": {"fulltext": "THE DESIGN OF MACHINES. 245\\nwhere A t is the net iron cross-section of the teeth under\\none pole corrected for fringing. The reluctance, the flux\\nthrough which must be maintained by the field-windings\\non one pole, is made up of a bi-parallel path in the arma-\\nture and a bi-parallel path in the field frame, both arranged\\nin series with the pole, the gap, and the tooth reluctances.\\nThis reluctance is equal to\\n(R, (R,\\n2 p y 2\\nXV. Magneto-motive force. The ampere turns per\\npole nl sh necessary to produce the flux f a in the armature\\nat no load is equal to\\n(R g (R, X(R p f\\nThese ampere turns are furnished by the shunt coil on\\none pole.\\nXVI. Shunt Coils. Assuming that E h volts are con-\\nsumed in the field regulating rheostat,\\nII K^l\\njR b\\n^2/ circular mils\\nWhence,\\nrx.i ii.znf th L h 2 fi\\nThe cross-section in circular mils\\nE E h\\nWhere n number of turns in shunt coil,\\nI sh the current in the shunt at no load, and\\nl sh the mean length of one field turn in feet.\\nAssuming 1,000 circular mils per ampere in the shunt coil,\\ncircular mils\\nI sh and\\n1000\\n1000 nL h\\ncircular mils", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0257.jp2"}, "258": {"fulltext": "246 DYNAMO ELECTRIC MACHINERY.\\nFrom a wire table the space occupied by the n turns can\\nbe attained and, with due allowance for insulation, refer-\\nence to the preliminary drawing will enable one to deter-\\nmine whether the assumed length of the pole l p is too\\nsmall or too great. Space must be left for the compound\\ncoil. This occupies about one-half as much space as the\\nshunt coil. If l p seems of unsuitable length it should be\\naltered, and the calculation should be again gone over.\\nXVII. Compound Coils. The method of calculating\\nthe number of compounding turns is so similar to that in\\nthe case of shunt coils that it need not be gone into in\\ndetail. The compound coils have to compensate at full\\nload for drop in the armature, for drop in the series coil,\\nfor drop in the line in case of overcompounding, for the\\ndemagnetizing armature ampere turns, and for changes in\\nreluctance due to skew by saturation. The back armature\\nampere turns, when multiplied by the coefficient of mag-\\nnetic leakage, give the series ampere turns necessary to\\ncompensate for them. It should be borne in mind that\\nthe maximum possible lead brings the brush no farther\\nthan the pole tip. To compensate for a drop of a certain\\npercentage requires that the density in the air gap be\\nraised by that same percentage. This necessitates an\\nincrease of all the densities. The increase of each reluc-\\ntance and the increase of each corresponding flux must be\\ncared for by the series windings. The coefficient of mag-\\nnetic leakage varies with the load. The manner of its\\nvariation may be unknown. The reluctances, into which\\nit enters, are such a small per cent of the total, that its\\nvariation may often be neglected.\\nThe following blank form, to be filled in by students in\\ndesigning, is self-explanatory.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0258.jp2"}, "259": {"fulltext": "THE DESIGN OF MACHINES.\\n247\\nPOLYTECHNIC INSTITUTE OF BROOKLYN.\\nDEPARTMENT OF ELECTRICAL ENGINEERING.\\nData sheet to be filled in by students taking Electrical Engineering 8, and\\ncovering the work of the first semester. This must be accompanied by the\\nfollowing scale drawings end elevatioji, longitudinal cross-section, plan, and\\nimportant details. A diagram of the ar?nature-winding must also be given.\\nAssumed values are to be entered in red ink.\\n.Designer\\nSubmitted.\\n9-\\n10.\\n11.\\n12.\\n13-\\n14.\\n16.\\n17.\\n18.\\n19.\\n20.\\n21.\\n22.\\nSPECIFICATIONS.\\nType of Machine\\nNumber of poles\\nCapacity in kilowatts\\nTerminal volts at no load\\nTerminal volts at full load\\nAmperes at full load\\nRevolutions per minute\\nMATERIALS.\\nArmature core\\nArmature spider\\nArmature end plates\\nArmature shaft\\nCommutator segments\\nCommutator spider\\nMagnet frame\\nPole piece\\nPole shoe\\nBrushes\\nBrush-holders\\nBrush-holder yoke\\nCommutator insulation\\nArmature conductor insulation\\nField-coil insulation\\nDIMENSIONS.\\nArmature.\\n23. Diameter over all\\n24. Diameter at bottom of slots\\nInternal diameter of core\\nLength over conductors\\nLength of core over laminations\\nand ducts\\nNet length of iron\\n29. Number of ventilating-ducts\\n30. Width of each ventilating-duct\\nThickness of sheets\\nNumber of slots\\nDepth of slots\\nWidth of slot at root\\nWidth of slot at surface\\nWidth of tooth at root\\nWidth of tooth at armature\\nface\\nSize and shape of bare con-\\nductor\\nSize of conductor insulated\\nPitch of winding, No. of teeth\\nArrangement of wires or bars\\nper slot\\n42. Number in parallel per slot\\n43. Number in series per slot\\n44. Total insulation between con-\\nductors\\n45. Thickness insulation between\\nconductors\\nAir Gap.\\n46. Length in center\\n25.\\n26.\\n28.\\n3 1\\n32.\\n33*\\n34-\\n35-\\n36.\\n37.\\n38.\\n39-\\n40.\\n41.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0259.jp2"}, "260": {"fulltext": "248\\nDYNAMO ELECTRIC MACHINERY.\\n47. Length maximum\\n48. Bore of field\\n49. Minimum clearance\\nPole Shoe.\\n50. Length parallel to shaft\\n51. Length of maximum arc\\n52. Length of minimum arc\\n53. Minimum thickness\\nPoles.\\n54. Length of pole\\n55. Width or diameter of pole\\n56. Lenpth parallel to shaft\\nMagnet Spool.\\n57. Number of spools\\n58. Length over all\\n59. Length of winding-space\\n60. Depth of win ding- space\\nMagnet Frame.\\n61. External diameter\\n62. Internal diameter\\n63. Thickness\\n64. Diameter over ribs\\n65. Thickness of ribs\\n66. Length along armature\\nCommutator.\\n67. Diameter\\n68. Number of segments\\n69. Width of segment at commu-\\ntator face\\n70. Width of segment at root\\n71. Useful depth of segment\\n72. Thickness of mica insulation\\n73. Available length of surface of\\nsegments\\n74. Total length of commutator\\n75. Peripheral speed\\nBrushes.\\n76. Number of sets of brushes\\n77. Number in one set\\n78. Length\\n79. Width\\n80. Thickness\\n81. Area of contact one brush\\nELECTRICAL.\\nArn ature.\\n82. Voltage at no load\\n83. Total voltage at full load\\n84. Total current\\n85. Number of sections\\n86. Turns per section\\n87. Number of layers\\n88. Total number of inductors\\n89. Type of winding circuits\\n90. Style of winding\\n91. Circular mils per ampere\\n92. Mean length of one turn\\n93. Total length of arm wire\\n94. Resistance of armature cold at\\n20 C. ohms\\n95. Resistance of armature hot at\\n70 C. ohms\\nShunt Coils.\\n96 Size of wire, No. B. S. Gauge\\n97. Turns per layer\\n98. No. of layers\\n99. Turns per spool\\n100. Mean length of one turn\\n101. Total turns\\n102. Total length of wire\\n103. Total weight of wire\\n104. Total resistance at 20 C.\\nohms\\n105. Total resistance at 70 C.\\nohms.\\n106. Volts allowed for rheostat\\n107. Maximum current am-\\nperes\\n108. Total ampere turns\\n109. Circular mils per ampere", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0260.jp2"}, "261": {"fulltext": "THE DESIGN OF MACHINES.\\n249\\nno.\\n1 11.\\n112.\\n3-\\n114.\\n115.\\n116.\\n117.\\n118.\\n119.\\n120.\\n122.\\n123.\\nSeries Coils.\\nSize and shape of conductor\\nNumber of conductors in mul\\ntiple\\nArrangement\\nTurns per layer\\nNumber of layers\\nTurns per spool\\nMean length of one turn\\nTotal turns\\nTotal length of conductor\\nTotal resistance at 20 C.\\nohms.\\nTotal resistance at 70 C.\\nohms.\\nMaximum current am-\\nperes\\nTotal ampere turns\\nCircular mils per ampere\\nHEATING,\\nArmature,\\n124. Area of drum radiating sur-\\nface sq. in.\\n125. Area each end radiating sur-\\nface sq. in,\\n126. Total radiating surface\\nsq. in.\\n127. 7 2 ^full load watts\\n128 Hysteresis watts\\n129. Eddy currents watts\\n130. Total watts\\n131. Total PR and core loss at\\nfull load watts\\n132. Watts persq. in. radiating sur-\\nface, full load\\n133. Estimated rise of temperature\\nat full load C.\\n134. Friction of windage and bear-\\nings watts\\nField Coils.\\n135. Radiating surface (heads)\\nsq. in,\\n136. Radiating surface (periphery)\\nsq. in.\\n137. Total radiating surface\\nsq. in.\\n138. PR shunt coils and rheostat\\nwatts\\n139. 7 2 R series watts\\n140. Total PR watts\\n141. Watts loss per sq. in, radi-\\nating surface\\n142. Estimated rise of temperature\\nat full load C.\\nCommutator,\\n143. Brush friction watts\\n144. Brush contact watts\\n145. Other commutator losses\\nwatts\\nMAGNETIC.\\n146. 0 at open circuit\\n147. (f a at full load\\n148. Leakage coefficient\\n149. f)f at open circuit 4 f at\\nfull load\\n150. Ampere turns required for\\nshunt\\n151. Ampere turns required for\\nseries", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0261.jp2"}, "262": {"fulltext": "250 RELUCTANCES AND AMPERE TURNS PER POLE.\\np o\\n\u00c2\u00a30\\n5u\\ns5\\n\u00e2\u0096\u00a0avo\\n\u00e2\u0096\u00a0avo r i\\n-a\\n3\\nU\\n0)\\nCD n O 12\\ns- cd d\\ncn\\nr S bo\\nG\\nU rt u\\nG\\nu fe g S\\n1\\n5\\n43 d) Cj\\n0)\\nArma\\nPole\\nMagn\\nAir G\\nTeeth\\nN rOrJ- vr 0 t^\\n00\\nLO lo ur i/- lo uo\\nM M \u00c2\u00bb-f I\u00e2\u0080\u0094 1 HH h- 1\\no\\nH\\nT3\\nO\\nT3 G\\ncd u\\nO o\\nG\\nO\\noj cd\\n\u00e2\u0096\u00a08\\nS\\nG rt\\no .a\\na\\no rt\\nG T3\\nO OS\\nu O\\ncS\\n7)\\nG\\ncd\\n.5\\nTj\\nTJ\\ncd\\nr-\\ncd\\n73\\ncd\\njj\\n3\\nCO\\nn\\nG\\nrrl\\nni\\nG\\n3\\ncd\\nen\\n(7)\\nCD\\nSi\\nif)\\ncd\\ncn\\nen\\nO\\nen\\nU\\nOh\\ncn\\nG\\nO\\nG\\nO\\nen\\n^0\\ncd\\ncn\\nu\\nCD\\ncd\\nc3\\nC J\\nG\\n0)\\nO\\nO\\nH\\nH\\nw\\nu\\nOn\\nHH\\nN\\n10 VO\\nVO\\nO", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0262.jp2"}, "263": {"fulltext": "TESTS.\\n251\\nCHAPTER XIV.\\nTESTS.\\n122. Determination of a (B-3C Curve. The most exact\\nlaboratory method of finding this curve is by the ballistic\\ngalvanometer or ring method. Fig. 1 79 shows the arrange-\\nment of apparatus for this\\nmethod. X is the test piece in\\nthe form of an annular ring, hav-\\ning a mean circumference of\\ncentimeters and a radial cross-\\nsection of a sq. centimeters. It\\nis wound uniformly with n prim-\\nary turns of wire. Over these\\nthree or four secondary test turns\\nof wire lead off to the ballistic\\ngalvanometer G. A series cir-\\ncuit is formed of a storage bat-\\ntery or other suitable source of\\nE. M. E, B, a variable resistance R, the primary coil of\\nthe test piece, an ammeter A, and a commutating switch C.\\nThe last is used for reversing the direction of the current\\nin the primary coil.\\nIf R be adjusted to give a current then the magne-\\ntizing force, or 3C, by 2 1 is represented by the formula\\n4.7ml\\nFig. 179.\\n3C\\n10/", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0263.jp2"}, "264": {"fulltext": "252\\nDYNAMO ELECTRIC MACHINERY.\\nIf now the current be suddenly commutated, all the lines of\\nforce will be withdrawn, and as many more set up in the\\nopposite direction. Each of these lines will induce, upon\\ncommutation, a pressure in each turn of the test coil.\\nThis induced E.M.F. furnishes a means of measuring the\\nflux of lines in the test piece or the flux density By\\napplication of the formula given in 16, one may obtain\\nthe expression for this quantity,\\n(B\\nio 8\\n2 an 9\\nk6.\\nWhere\\nJ? t the resistance of the test coil, the galvanometer, and\\nthe secondary circuit\\na the area of a radial section of the test piece in\\nsquare centimeters\\nn 2 the number of turns in the test coil\\nk a constant of the galvanometer; and\\nthe throw of the galvanometer which accompanies the\\ncommutation of the primary current.\\nThough the most accurate method, the ring method is\\nnot generally employed in commercial practice because of\\nthe cost and the time re-\\nquired in preparing a test\\n-storage piece,\\nCELLS\\nLENGTH\\nPIECE\\nBALLISTIC\\nGALVANOMETER\\nThe divided-bar method\\nadmits of the use of a bar\\nof iron of ordinary shape as\\na test piece. This is cut\\ninto two pieces. A heavy\\nwrought-iron yoke, Fig. 180, has a magnetizing coil wound\\ninside of it. Through snug-fitting holes in the ends of\\nthe yoke, the two halves of the test piece are inserted,\\nFig. 180.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0264.jp2"}, "265": {"fulltext": "TESTS.\\n253\\none being secured, and the other being fitted with a\\nhandle. The test coil is so mounted on springs as to\\nfly suddenly to one side when the test pieces are slightly\\nseparated by a pull on the handle. It thus cuts all\\nthe flux in the piece, and affords a means of measuring\\nit. The yoke is so massive, and has such a small reluc-\\ntance as compared with that of the test piece, that the\\nformula 3C -is practically true, where is the mean\\n10\\nlength of the test piece which is traversed by magnetic\\nlines. For (B the formula is twice what it was in the\\nring method, since the test coil cuts the flux but once, or\\nB\\nThe method of reversals could be used equally well with\\nthis apparatus, requiring the formula used in the ring\\nmethod.\\nThe permeameter is a machine for measuring the flux in\\na test piece by measuring the force necessary to detach it\\nfrom another part of the magnetic cir-\\ncuit. Fig. 1 8 1 shows in simple such a\\nmachine. The magnetizing force is\\nsupplied by the coil C the same as in\\nthe divided bar method. The test coil\\nand galvanometer are done away with.\\nThe bottom of the yoke Y is surfaced\\nto receive flatly the end of the test rod\\nT. When the proper current is flow-\\ning in the coil, the force necessary to\\nseparate the test piece from the yoke is found by means of\\nthe spring-balance 5. Since the force required to break\\nFig. 181.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0265.jp2"}, "266": {"fulltext": "254 DYNAMO ELECTRIC MACHINERY.\\nany number of lines of force varies as the square of that\\nnumber, it is easy to calculate the flux, and since\\n=.area X (B,\\nthe magnetic density is readily found. The value of 3C is\\nobtained as in the preceding case.\\n123. Determination of the Ballistic Constant. The\\nstandard condenser affords the most convenient and accu-\\nrate means of determining the constant of a ballistic gal-\\nvanometer. If the capacity of the condenser C, and the\\nvoltage at which it is charged E, be known, then the quan-\\ntity of electricity that will flow when the circuit is closed\\nthrough the galvanometer is also known. It is equal to\\nEC. By observing the galvanometer throw 0, the value of\\nthe constant k is determined from\\nThe coil of a d Arsonval ballistic galvanometer moving in\\nits field has an E.M.F. induced in it, which tends to send\\na current in a direction opposite to that of the current that\\nproduces the throw, and which, therefore, shortens the\\nthrow or damps the galvanometer. The magnitude of this\\ndamping current depends, of course, on the resistance of\\nthe galvanometer circuit hence the constant k should be\\ndetermined with the same external resistance in the gal-\\nvanometer circuit as there will be when the test for the\\nvalue of is being made.\\nTo accomplish this an arrangement of apparatus such as\\nis shown in Fig. 182, may be employed, the particular fea-\\nture of which is the quadruple contact key. This key is", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0266.jp2"}, "267": {"fulltext": "TESTS.\\n255\\nnormally held up against a contact. In this position the\\ngalvanometer circuit is open, and the condenser is in series\\nwith a charging battery.\\nAs the key is pressed down, 1 1\\nthree things occur. First\\nthe battery circuit is broken,\\nthen the condenser is dis-\\ncharged through the gal-\\nvanometer, and lastly the\\ngalvanometer circuit is\\nclosed through an appro-\\npriate amount of resistance\\nin the rheostat.\\nThe ballistic constant may also be determined by the\\nuse of a long solenoid, with a few turns about its center\\nfor a test coil. A series circuit is formed (Fig. 183) of\\na battery, a variable resistance, an ammeter, the solenoid,\\ni\\nFig. 182.\\nFig. 183.\\nand a key. The ends of the test coil are attached to the\\ngalvanometer through proper resistance. On closing the\\ncircuit the current sets up a field at the center of the\\nsolenoid, whose intensity,\\n4.7m I\\n0C\\njo/", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0267.jp2"}, "268": {"fulltext": "256 DYNAMO ELECTRIC MACHINERY.\\nwhere is the length of the solenoid in centimeters, and n\\nthe number of primary turns.\\nIf A be the area in square centimeters of a cross-section\\nof the solenoid perpendicular to the axis, then\\n3CA.\\nIf n 2 be the number of turns in the test coil, and R be\\nthe resistance of the galvanometer circuit in ohms, then\\nupon closing the circuit and upon establishing the flux j y a\\nquantity of electricity will pass around the secondary cir-\\ncuit which is equal to\\nn bfi n 4 imn IA\\nwhere 8 is the throw of the galvanometer corresponding to\\nthe current Therefore,\\nk\\n^irnn^IA\\nio 9 J?/0\\nIf the solenoid be less than ten diameters long, this result\\nis not accurate, owing to the influence of the ends of the\\nsolenoid upon the value of JC.\\nThere have been described numerous methods for deter-\\nmining k which depend upon a constant and definite inten-\\nsity of the earth s magnetic field. Nowadays the fact\\nthat the earth s field is constantly changing, both in direc-\\ntion and magnitude, due to the prevalence of iron and steel\\nbuildings, and the extensive use of electric currents for\\ntrolley, lighting, and other purposes, makes these methods\\npractically worthless.\\n124. Determination of the Hysteretic Constant. The\\nhysteresis curve for any sample of iron may be found most\\naccurately by the step-by-step method. The arrangement\\nof apparatus is in all respects similar to that of Fig. 179,", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0268.jp2"}, "269": {"fulltext": "TESTS.\\n257\\nsave that the rheostat R must be so designed that the cir-\\ncuit does not open, even for an instant, in passing from\\none resistance point to another. The method of operation\\nis as follows The rheostat is set for a maximum current\\nstrength which is determined by means of an ammeter.\\nThe rheostat handle is then quickly moved back one point.\\nThis reduces the current and the dependent magnetizing\\nforce proportionately. There is an accompanying decrease\\nof flux in the sample. This decrease is determined by the\\ngalvanometer throw, the formula being as before,\\nio 8 T/\\nChange in (B kv.\\nThe ammeter current is again read and, as soon as the\\ngalvanometer comes to rest, the resistance is increased by\\nanother step, and the throw of the galvanometer is observed.\\nAfter the current has been reduced step by step to zero, it\\nis then commutated, and increased by steps until the maxi-\\nmum magnetization is obtained in a direction opposite to\\nthat at the beginning. The current is again cut down by\\nsteps to zero, is afterwards commutated for a second time,\\nand is again increased until the magnetic condition of the\\niron which prevailed at the start is again attained. Giving\\nto (B a plus or minus sign, according to the direction of the\\ngalvanometer throw, the algebraic sum of all the changes\\nof (ft must equal zero. Therefore the algebraic sum of\\nall the galvanometer throws should equal zero. A simple\\naddition serves as a check on all observations. In practice,\\nthe sum of the plus throws may differ from the sum of the\\nminus ones by three per cent without seriously affecting the\\nfinal result. Having the maximum value of (B, the s cor-\\nresponding to each can readily be found by subtracting the", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0269.jp2"}, "270": {"fulltext": "258\\nDYNAMO ELECTRIC MACHINERY.\\nchanges in (B from the maximum Upon plotting a cyclic\\ncurve of the various values of and the corresponding\\nvalues of JC, one obtains a hysteresis loop, as in Fig. 184.\\nThe area of this loop in (ftX units, when divided by 4?r, gives\\nthe ergs loss of energy in carrying one cubic centimeter of\\nthe iron under test through a cycle of magnetization be-\\ntween the limits of max and max According to the\\nSteinmetz formula,\\nwhere h is the loss by hysteresis in ergs per cycle per cubic\\ncentimeter. Hence, to find the hysteresis constant rj of\\nthe sample used in the foregoing test, one uses the formula\\nA h\\nwhere A h area of hysteresis curve expressed in (B3C units,\\nand V volume of iron in cubic centimeters.\\nFig. 184.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0270.jp2"}, "271": {"fulltext": "TESTS.\\n259\\nA much less laborious method of measuring rj, and one\\nwhich does not introduce the errors attending the measure-\\nment of the area of a curve, is the wattmeter method. Since\\nthe iron to be tested is generally for use in alternating cur-\\nrent apparatus, this method has the additional advantage\\nthat the test occurs under the conditions which the iron\\nwill meet in its working.\\nIf the ring be made of annular stampings of sheet metal\\nwell shellacked before assembling, then the loss due to eddy\\ncurrents will be negligible. The arrangement of apparatus,\\nshown in Fig. 185, consists of a source of alternating cur-\\nrent, a wattmeter, an alternating current ammeter, an alter-\\nnating current voltmeter, and the test ring, all connected\\nas shown.\\nFig. 185.\\nLet R the resistance of the coil on the test ring\\nn number of turns in this coil\\nW the watts indicated by the wattmeter\\nthe current indicated by the ammeter;\\nE the pressure indicated by the voltmeter\\nV= the volume of the iron in cubic centimeters;\\nA the area of a radial cross-section in square centi-\\nmeters then, assuming the current to be sinus-\\noidal, and of frequency /cycles per second,\\n_ io 7 W 7 2 R) I \\\\l27rnfA\\nVf\\nI V2 irn/AV\\nE10*", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0271.jp2"}, "272": {"fulltext": "260\\nDYNAMO ELECTRIC MACHINERY.\\nE wing s machine for hysteresis tests is shown in Fig. 186.\\nIts chief advantage lies in the fact that the test piece needs\\nto consist of but half a dozen pieces of sheet iron f by 3\\nThis test piece is made to rotate be-\\ntween the poles of a permanent mag-\\nnet, which is mounted on knife edges\\non an axis coincident with the axis of\\nrevolution of the test piece. The re-\\nsulting angular displacement of the\\nmagnet, as marked by a pointer on a\\ndivided scale, is proportional to the\\nhysteresis loss in the specimen. A\\ncalibration curve is plotted by using\\ntwo different specimens having known\\nFig. 186. hysteretic constants. It is found that\\nsmall variations in the thickness of the test piece do not\\naffect the results, and that no correction need be made\\nfor such variations. The machine yields but comparative\\nresults.\\n125. Determination of Leakage Coefficient. The ratio\\nof the total flux generated by a field magnet to the flux\\npassing through the armature, that is, the leakage coefficient,\\nwhich is always greater than unity, may be found with an\\narrangement of apparatus as shown in Fig. 187 where the\\nmachine is a yoke-wound bipolar. A test coil of a few\\nturns is passed around the center of the field magnet, and\\nthrough it all the lines generated may reasonably be as-\\nsumed to pass. A similar coil is passed around the arma-\\nture, in a plane perpendicular to the direction of the flux,\\nthrough which all the armature flux must pass. In the\\ncase of a small machine, normal exciting current is passed", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0272.jp2"}, "273": {"fulltext": "TESTS.\\n26l\\nthrough the field magnet, with arrangements for rapid com-\\nmutation. In this case, if one test coil have its ends\\nattached to a galvanometer or a low-voltage voltmeter, and\\nif the current in the field coil be commutated, a deflection,\\nwhich is proportional to the change of flux, will be observed.\\nThe same will happen if the other coil have its terminals\\nconnected to the galvan-\\nIf 6 f and e t\\nometer,\\nthe deflections\\nwith the field\\narmature test coils\\nspectively, then, as\\nfore,\\nIO 8\\nbe\\nobserved\\nand the\\nre-\\nbe-\\nf f (By\\nt a\\nkQ f and\\nv\u00c2\u00bb\\nio 8 i?\\n2 /Zo\\nkO a\\nFig. 187.\\nIf the two test coils be constructed alike as regards number\\nof turns and resistance, then the values of i?, /z 2 and k are\\nthe same in both equations, and we have the leakage coef-\\nficient\\nh 0/\\n4 0*\\nHence the ratio of the galvanometer throws gives the co-\\nefficient without further calculation.\\nThis method may be employed to obtain the flux in any\\npart of the magnetic circuit, and it serves to locate the\\npoints of greatest leakage. It may also be modified to apply\\nto any type of machine. In the case of large machines,\\nwhose field currents cannot be commutated, a cyclic in-\\ncrease and decrease of exciting current can be produced\\nby means of cutting out and in of resistance in the field", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0273.jp2"}, "274": {"fulltext": "262\\nDYNAMO ELECTRIC MACHINERY.\\ncircuit. Even then the time constants of large field coils\\nare so great as compared with the period of swing of ballis-\\ntic galvanometers, that the method is impracticable.\\n126. Magnetic Distribution in the Air Gap. Since ar-\\nmature reactions distort the magnetic field, it is desirable\\nto know the actual distribution of the flux. This may be\\nFig. 188.\\ndetermined by the use of a pilot brush, as shown in Fig.\\n188. A voltmeter is connected between one of the main\\nbrushes and the pilot brush, and the latter is moved\\nthrough equal angular intervals until the opposite brush\\nis reached. The difference in the voltage of any two\\nconsecutive readings is proportional to the magnetic flux\\nwithin the angular distance moved over between those\\ntwo readings.\\nTwo pilot brushes may be used as in Fig. 1 89. In this\\ncase the voltage is proportional to the flux corresponding\\nto the angular distance between the two brushes. By", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0274.jp2"}, "275": {"fulltext": "TESTS.\\n263\\napplying these brushes at successive intervals through\\n180 the flux distribution can be determined.\\n127. Measurement of Resistance a. By voltmeter alone.\\nFor insulation resistances, or any resistances lying between\\nabout 5000 and 100,000 ohms, a fairly accurate result may\\nbe obtained by arranging the unknown resistance x and a\\n0-150 voltmeter in series with a source of constant potential\\nof about 115 volts. The reading 6 is noted. The resist-\\nance is then short-circuited and the deflection ff noted. If\\nR be the resistance of the voltmeter, then\\nff-0\\nR.\\nMaximum accuracy is obtained when x R.\\nAVWWWM1\\nn r r\\nFig. 190.\\nb. By the Method of Wheatstone s Bridge. If an un-\\nknown resistance x two known resistances a and b, and\\na known adjustable resistance R be connected as shown\\nin Fig. 191, with a galvanometer G and a battery cell B,\\na Wheatstone s bridge is formed; and, if the resistance R\\nbe so manipulated as to prevent a flow of current through\\nthe galvanometer, then the following relation is true\\na b R x.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0275.jp2"}, "276": {"fulltext": "264\\nDYNAMO ELECTRIC MACHINERY.\\nIt is usual to make the ratio a b equal to some multiple\\nor submultiple of 10. In this case the value of Xis read\\ndirectly from R with the decimal point suitably placed.\\nThis method permits of great accuracy.\\nC. By ammeter and voltmeter. Resistances of ordinary\\nmagnitudes are most conveniently measured by measuring\\nthe pressure impressed on the resistance and the current\\ncaused to flow thereby. This is the most practical method\\nfor finding the resistances of armature and field-windings\\nof dynamos.\\nIt is a method so rapid that the value of hot re-\\nsistances may be found, and fields can be measured even\\na\\nsr\\nFig. 192.\\nwhile the machine is in operation. Fig. 192 shows an\\narrangement of apparatus for measuring the resistance of\\nan armature, including the brush and contact resistances.\\nIf be the ammeter reading, and E be the voltmeter read-\\ning, then by Ohm s law\\nR\\nE\\n7\\n128. Test of Dielectric Strength In order to test the\\nvoltage necessary to break down a sample sheet of insulat-\\ning material, the sample is placed between two flat metal-\\nlic surfaces, which are connected respectively with the two\\nterminals of a high-voltage transformer, whose voltage can\\nbe varied at will. An air gap between needle-point ter-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0276.jp2"}, "277": {"fulltext": "TESTS.\\n265\\nminals which can be adjusted in length is connected in\\nparallel between the two terminals. The distance between\\nthese points serves to limit the voltage which can be im-\\npressed upon the conductors on each side of the insulating\\nmaterial. For small variations of gap length the voltage\\nnecessary to produce an arc between the needle-points is\\n56\\n54\\n52\\n50\\n48\\n16\\n44\\n42\\n40\\n38\\n2\\n2,\\nA\\n2.\\n6\\n2\\n8\\nI\\n3\\n2\\n3\\n4\\n3.\\nG\\n3.\\n8\\n4\\n36\\n34\\n32\\n\u00c2\u00a330\\n28\\n2 20\\n24\\n22\\n20\\n18\\n16\\n14\\n12\\n10\\nS\\n6\\n4\\n2\\ni\\n2\\n1\\n5\\n8\\n1\\nMCH\\n1.\\n1ES\\n1\\n.2\\n1\\n4\\n1\\n6\\n1\\n8\\n2\\nFig. 193.\\nnearly proportional to the length. The following table,\\ntaken from the Standardization Report of the American In-\\nstitute of Electrical Engineers, shows the relation which\\nexists between air-gap length and the voltage necessary\\nto produce a disruptive discharge. The relations are also\\nexhibited in the curve of Fig. 193.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0277.jp2"}, "278": {"fulltext": "266\\nDYNAMO ELECTRIC MACHINERY.\\nTABLE OF SPARKING DISTANCES IN AIR BETWEEN\\nOPPOSED SHARP NEEDLE-POINTS, FOR VARI-\\nOUS EFFECTIVE SINUSOIDAL VOLTAGES,\\nIN INCHES AND IN CENTIMETERS.\\nKlLOVOLTS.\\nDistance.\\nKlLOVOLTS.\\nDistance.\\nSq. Root of\\nMean Square.\\nInches.\\nCms.\\nSq. Root of\\nMean Square.\\nInches.\\nCms.\\n5\\nIO\\nJ 5\\n20\\n25\\n3\u00c2\u00b0\\n35\\n40\\n45\\n5o\\nO.225\\nO.47\\nO.725\\n1.0\\ni-3\\n1.625\\n2.0\\n2.45\\n2.95\\n3-55\\nO.57\\nI.I9\\nI.84\\n2.54\\n3-3\\n4.1\\n5-i\\n6.2\\n7.5\\n9.0\\n60\\n70\\n80\\n90\\n100\\nno\\n120\\nI30\\n140\\nI50\\n4.65\\n5.85\\n7-1\\n8-35\\n9.6\\nIO.75\\nII.85\\n12.95\\n13-95\\n15.O\\n11.8\\n14.9\\n18.0\\n21.2\\n24.4\\n27.3\\n30.1\\n32.9\\n354\\n38.1\\nIn carrying out the test, the needle-points are adjusted\\nat a certain minimum distance apart. The voltage im-\\npressed upon the terminals is raised until a spark passes\\nbetween the points. The air gap is then increased in\\nlength, and the operation repeated until the sample breaks\\ndown, and the spark passes through it instead of across\\nthe air gap. The break-down voltage is then taken from\\nthe table or curve corresponding to the last position of the\\nneedle-points.\\nThe sample should project considerably beyond the\\nedges of the compressing surfaces. Owing to surface\\nleakage a spark will pass over a very much greater distance\\nof the surface of an insulator than it will in free air.\\nFor the purpose of obtaining a voltage any form of high-\\npotential transformer may be used, the primary being sup-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0278.jp2"}, "279": {"fulltext": "TESTS.\\n267\\nplied by an alternating current. Fig. 194 illustrates a\\n10,000 volt transformer manufactured for this purpose by\\nthe General Electric Co. Its core is of the H type, and\\nFig. 194.\\nupon one branch of it is wound the low-tension circuit,\\nwhile upon the other is wound the secondary, consisting of\\nfour coils, each wound and insulated independently. The\\nfour coils are assembled upon a sleeve of heavy insulating", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0279.jp2"}, "280": {"fulltext": "268\\nDYNAMO ELECTRIC MACHINERY.\\nmaterial. The transformer is immersed in oil, and its\\nprimary is wound in two parts so that it may be used upon\\na 52 or a 104 volt circuit. The adaptation to either of\\nthese circuits is rendered possible by means of a porcelain\\nseries multiple connection board which is placed inside the\\ninclosing case. On the top of the apparatus is a box with\\na glass window, which incloses a micrometer spark gap,\\nwhich is connected in shunt across the high-potential\\n?L\\nr=5T\\nFig. i95.\\nterminals. This box or cover carries\\nfour long contact studs which fit into\\nsockets. In the transformer box the\\napparatus is so arranged that the lifting\\nup of this cover for the purpose of ad-\\njusting the spark gap entirely discon-\\nnects the spark gap from the high-potential circuit. The\\nconnections of this apparatus to a sample under test are\\nshown in Fig. 195.\\nThis apparatus may also be employed in determining\\nwhether a given sample of insulation will withstand an im-\\npressed electromotive force without breaking down. The", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0280.jp2"}, "281": {"fulltext": "TESTS.\\n269\\nlength of the gap is set so as to represent the value of the\\nprescribed electromotive force, and the sample is subjected\\nto the pressure which maintains a spark across the gap.\\nIn case of break-down the spark at the gap will cease.\\nIn case it is desired to test the dielectric strength of the\\nsample at some other than normal temperature, the sample\\nmay be pressed between two surfaces of the apparatus\\nshown in Fig. 196, which was described by Mr. Charles F.\\nFig. 196.\\nScott. Two carefully faced blocks of cast iron are re-\\ncessed so as to receive coils D and D of asbestos-wound\\nwire. These coils are supplied with alternating current\\nwhich raises the temperature of the disks by means of\\neddy currents and hysteresis losses. Upon shutting off\\nthe current, the disks and insulating material soon assume\\na uniform temperature, which can be measured by means\\nof a thermometer whose bulb is inserted in a hole in the\\nupper disk. The two disks are made the terminals of the\\nhigh-tension circuit. Connections with the circuit which\\nis used for heating purposes must of course be removed\\nduring the test.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0281.jp2"}, "282": {"fulltext": "270 DYNAMO ELECTRIC MACHINERY.\\nThe report of the committee on standardization of the\\nAmerican Institute of Electrical Engineers gives the fol-\\nlowing The dielectric strength or resistance to rup-\\nture should be determined by a continued application of an\\nalternating E.M.F. for five minutes.\\nThe test for dielectric strength should be made with\\nthe completely assembled apparatus and not with its indi-\\nvidual parts, and the voltage should be applied as fol-\\nlows 1st, Between electric circuits and surrounding\\nconducting material, and 2d, between adjacent electric cir-\\ncuits where such exist.\\nThe report further recommends for apparatus, not in-\\ncluding switchboards and transmission lines, the following\\ntesting voltages\\nRATED TERMINAL VOLTAGE. CAPACITY. TESTING VOLTAGE.\\nNot exceeding 400 volts Under 10 k.w. 1000 volts.\\nNot exceeding 400 volts 10 K.w. and over\\n400 and over, but less than 200 volts Under 10 k.w.\\n400 and over, but less than 800 volts 10 k.w. and over\\n800 and over, but less than 1200 volts Any\\n1200 and over, but less than 2500 volts Any\\n1500 volts.\\n1500 volts.\\n2000 volts.\\n3500 volts.\\n5000 volts.\\nDouble the normal\\n2 coo and over Any\\nrated voltages.\\nSynchronous motor fields and fields of converters started\\nfrom the alternating current side 5000 volts.\\nThe values in the table above are effective values, or square roots of\\nmean square reduced to a sine wave of E.M.F.\\nWhen machines or apparatus are to be operated in series, so as to em-\\nploy the sum of their separate E.M.F?\u00c2\u00a7, the voltage should be referred to\\nthis sum, except where the frames of the machines are separately insulated\\nboth from ground and from each other.\\n129. Determination of the Magnetization Curve of a\\nShunt-Dynamo To find the relation between the exciting\\ncurrent and the no-load terminal volts of a shunt machine,", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0282.jp2"}, "283": {"fulltext": "TESTS.\\n271\\nexcite tne shunt fields, Fig. 197, from an external source,\\nfirst passing the current through a variable resistance and\\nFig. 197.\\nan ammeter. Run the machine at a constant speed through-\\nout the test. If a voltmeter be placed across the armature\\nterminals a pressure can be read corresponding to each\\nexciting current, and a curve can be plotted using volts as\\nordinates and amperes as abscissae. Because of residual\\nFig. 198.\\nmagnetism there are some volts with no exciting current,\\nand hence the curve, Fig. 198, does not pass through the\\norigin.\\nIf the voltmeter be read while the current is increasing\\nby steps to the maximum, and again while the current is,", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0283.jp2"}, "284": {"fulltext": "272\\nDYNAMO ELECTRIC MACHINERY.\\ndecreasing, step by step, the two curves will not coincide\\nthe descending curve will lie above the other as in Fig. 199.\\nThis is because of the hysteresis or magnetic retentivity of\\nthe iron of the magnetic circuit.\\nFig. 199.\\n130. Efficiency of Dynamos and Motors. The efficiency\\nof these machines can be determined by any one of the\\nfollowing methods\\na. Run the machine at its proper speed as a separately\\nexcited motor. Let the excitation be normal. By means\\nof ammeter and voltmeter readings determine the electrical\\ninput, the motor having no load upon it. The arrange-\\nment of apparatus is shown in Fig. 200. The power put\\nin represents the PR losses in the armature and the field\\nplus the losses which are generally considered as constant\\nat al 1 loads. These constant losses are those due to fric-\\ntion, hysteresis, Foucault currents, and windage. They\\nare equal to the no-load input minus the no-load PR arma-\\nture and field losses. The PR losses can be calculated at", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0284.jp2"}, "285": {"fulltext": "TESTS.\\n273\\nany useful load. The efficiency at that load is equal to\\nthe load divided by the load plus the sum of the constant\\nSERVICE MAIN\\nSERVICE MAIN\\nFig. 200.\\nlosses and the load PR losses. The machine at the time\\nof no-load test should have the same temperature as it\\nwould have under the load for which the efficiency is being\\ncalculated.\\nb. Run the machine as a motor at its\\nrated speed and temperature. Measure\\nthe electrical input by a voltmeter and an\\nammeter. Measure the mechanical output\\nby a Prony brake. Then the efficiency,\\nwatts at brake\\nrj\\nwatts input\\nThere are many kinds of brake or ab-\\nsorption dynamometers that may be used\\nfor this test. The most satisfactory one Fig 201\\nfor motors of small size is the strap-brake shown in\\nFig. 201. A piece of leather belting and two spring\\nbalances are all that is necessary. The formula for the\\nabsorbed power is,\\nWatts\\n2TrrV{P-P\\nX 746,\\nwhere r\\n33000\\nthe radius of the pulley in feet", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0285.jp2"}, "286": {"fulltext": "274\\nDYNAMO ELECTRIC MACHINERY.\\nV= number of revolutions per minute\\n(P P the difference of the two-scale readings in\\npounds.\\nFig. 202 shows a form\\nof brake applicable to lar-\\nger machines. The for-\\nmula for the power ab-\\nsorbed is,\\nFig. 202.\\nWatts\\n2izrVP\\n33000\\nx 746,\\nwhere r is the perpendicular distance from the center of\\nthe pulley to the line of action of the scale in feet, P the\\nscale reading in pounds, and V the number of revolutions\\nper minute. The brake should be so poised as to give no\\nreading on the spring at no load.\\nThe brake may be made with a metal strap having\\nspaced blocks on its under surface that screw down against\\nthe wheel, and for the spring balance one may use a plat-\\nform scale having a prop extending to the lever arm of the\\nbrake. For large machines the heat generated by the\\nabsorption of considerable power at the face of the pulley\\ncauses an excessive rise of temperature. It is necessary\\nto find some means of carrying the heat away. This is\\ngenerally accomplished by flanging the inside of the brake-\\nwheel, forming a trough in which water is kept running.\\nCentrifugal force throws the water against the internal\\ncircumference of the wheel and prevents spilling. The\\nwater is removed either by a properly placed scoop, or it\\nmay be allowed to boil out.\\nc. A convenient method of finding and separating the\\nlosses of a machine is one which makes use of a rated", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0286.jp2"}, "287": {"fulltext": "TESTS. 275\\nmotor, i.e., a motor whose mechanical output is known for\\nany given electrical input. By reading the volt-ampere\\ninput of the motor the power expended on the machine to\\nbe tested can be found. Run the machine by the rated\\nmotor at the proper speed. If the brushes be removed\\nfrom the machine, and no current be flowing in the field\\ncoils, then the power expended on it is the loss due to\\nfriction at the bearings and to windage. Now let the\\nbrushes be set, then the power expended is the loss due to\\nwindage, bearing friction, and brush friction. By sub-\\ntraction the brush-friction loss is found. This is greater,\\nparticularly in small machines, than is generally supposed.\\nNow let the fields be separately excited by the normal\\ncurrent, and the losses due to hysteresis and eddy currents\\nare included in the power expended on the machine.\\nFrom a knowledge of the hot resistances of the machine,\\none can calculate the I 2 R loss for any useful load in both\\narmature and field windings. This useful load divided by\\nthe sum of the useful load and all the losses, gives the\\nefficiency of the machine at that load.\\nd. The methods a b, and c all require some outside\\nelectric power. This requirement can be avoided by the\\nuse of a transmission dynamometer to measure the power\\ninput of any machine, and the power output can be read by\\na voltmeter and an ammeter. This method is seldom re-\\nsorted to, since transmission dynamometers are often unre-\\nliable, they are expensive to set up, and some forms have\\nbut a limited power range.\\nProfessor Goldsborough has recently devised a very\\ningenious dynamometer which consists simply of a coiled\\nor helical spring with the center line of the helix corre-\\nsponding with the center of the shaft. This spring con-", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0287.jp2"}, "288": {"fulltext": "276 DYNAMO ELECTRIC MACHINERY.\\nnects the driving and driven members. Readings are made\\nby means of two instantaneous contact points mounted,\\none on the driven and one on the driving-shaft, which are\\nconnected in series with each other and with a battery\\nand telephone receiver. As the spring becomes deflected\\nby a load, the contact on the driven shaft falls back,\\nand the corresponding brush must be set back by the\\nsame angle in order to obtain a click in the telephone.\\nThis angle is a direct measurement of the torque, and can\\nbe calibrated at standstill.\\ne. The efficiency of direct connected units can be found\\nby using the indicator card from the steam-engine to deter-\\nmine the power input, and by using a voltmeter and an\\nammeter for determining the electrical output. Even if\\nthe engine losses were exactly known, the measurements\\nyielded by an indicator card are hardly exact enough to\\nafford a fair basis for testing the efficiency of a generator.\\nIn other than direct-connected units it is not frequent that\\none finds a generator driven by an engine that does no\\nother work.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0288.jp2"}, "289": {"fulltext": "INDEX.\\nAir-gap, 69, 8 1, 85.\\ndistribution in, 262, 87.\\nAmpere-turns, 21, 245.\\nAngle of lag or lead, 82.\\nArmatures, 34, 47, 51.\\nBack-turns, 82.\\nBearings, 64.\\nBoosters, 216.\\nBox, starting for motors, 169.\\nBrake on motors, 179.\\nprony, 273.\\nsolenoid, 182.\\nstrap, 180.\\nBrushes, 60, 61, 86, 90.\\nCandle-power of arc lamps, 130.\\nof incandescent lamps, 103.\\nCapacity of a dynamo, 36.\\nCauteries for surgeons, 215.\\nChord winding, 52.\\nCircuits, divided, 7, 8.\\nCoefficient\\neconomic, 93.\\nof series dynamo, 97.\\nof compound dynamo, 1 1 1\\nof shunt dynamo, 100.\\nof conversion, 93.\\nof magnetic leakage, 73, 260.\\nof self and mutual induction,\\n17, 18.\\nof temperature, 5.\\nCoercivity, 28.\\nCoil\\narmature, 46, 49.\\ncompound, 71, 246.\\nfield, 71.\\nformed, 55.\\nCollection of currents, 61.\\nCommutation, 84.\\nCommutator\\nconstruction of, 59.\\nlosses at, 59.\\nprinciple of, 32, 77.\\nsegments of, 33.\\nCompounding\\nin motor, 174, 224.\\nwindings for, 71, in.\\nConductivity, 5.\\nof copper, 6.\\nConnections\\nfor combined output, 218.\\nof motors, 223.\\nseries dynamos in series, 221.\\nshunt dynamos in parallel, 220.\\nshunt dynamos in series, 221.\\ncross in armature, 48.\\nConstant\\ndetermination of ballistic by\\ncondenser, 254.\\ndetermination of ballistic by\\nlong solenoid, 255.\\ndetermination of ballistic earth s\\nfield, 256.\\n277", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0289.jp2"}, "290": {"fulltext": "278\\nINDEX.\\nConstant\\ndetermination of hysteretic, 256,\\n259, 260.\\nhysteretic, 29.\\nContact of brushes, 60.\\nController\\nfor mill motors, 206.\\nfor street-railway motors 197.\\nfingers for, 198.\\nreversing lever, 199.\\nwipes, 198.\\nCore, armature, 3J, 57.\\nfield, 67.\\nCorrection for tooth densities, 243,\\nCross-magnetization, 80.\\nCurrent density, 72.\\nin armature, 234.\\nCurrents, foucault or eddy, 38, 90.\\nCurve, B-H., 24, 25, 244.\\ncharacteristic, 96, 98, 101, 174.\\ndetermination of B-H, 251.\\ndeterminization of magnetiza-\\ntion, 270.\\nDemagnetization, 82, 246.\\nDensity of flux, 22.\\nin air-gap, 233.\\ncorrections for, in teeth, 243.\\ndetermination of distribution\\nof, 262.\\nin field, 131, 241.\\nDesign, data sheet for, 247.\\ndifferent methods of, 232.\\nof armature, 235.\\nof field, 241.\\npreliminary assumption for, 233\\nspecifications for, 233.\\nDiameter of armature, 237.\\nof shaft, 64, 119.\\nDielectric test of insulation of, 268.\\ntest of strength of, 264, 270.\\nDirection of induced E. M. F., 16.\\nof rotation of a motor, 161.\\nDrop, 4.\\nDrums, 34, 5 1.\\nDynamo\\narc lighting, 129.\\nBrush, 134.\\nWestinghouse, 141.\\nWood, 143.\\nExcelsior, 147.\\nBall, 149.\\nThomson-Houston, 151.\\nWestern Electric Co., 156.\\ndefinition of, 31.\\ndirect-driven, 118.\\nBullock Electric Co., 127.\\nCrocker- Wheeler, 123.\\nGeneral Electric Co., 121.\\nLundell, 88, 124.\\nSprague Electric Co., 88, 124.\\nWestinghouse Co., 119.\\nDynamotors, 208.\\narmature, reaction in, 208.\\nfor Bullock teazer system, 209.\\nfor electrometallurgy, 211.\\nas rotary equalizer, 212.\\nfor telegraphic work, 213.\\nDyne, definition of, 1.\\nEfficiency, 92.\\nof compound dynamo, 112.\\nof compound motor, 165.\\ndetermination of, 272.\\nof direct connected units, 276.\\nof motors for automobiles, 202.\\nof shunt motors, 166.\\nof series motors, 166.\\nE. M. F. constant supply of,\\n103.\\ncounter in motors, 163.\\ndirection of induced, 16.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0290.jp2"}, "291": {"fulltext": "INDEX.\\n2 79\\nE. M. F.\\nin shunt dynamos, 100.\\nin separately excited dynamos,\\n95-\\nin series dynamos, 97.\\nof induction, 14.\\nof self and mutual induction,\\n17, 79. 84.\\nof eddy currents, 38.\\nprinciple of production of, in\\narmature, 32.\\nunit of, 3.\\nEnergy, 1, 89.\\nEqualizer, bus, 222.\\nrotary, 212.\\nErg, 1.\\nExcitation, mutual, 222.\\nseparate, 94.\\nof fields, 69.\\nFall, of potential, 4.\\nFeeding-points, 104.\\nField, magnetic, 12, 21, 67.\\nFleming s rule, 16.\\nFluctuation of E. M. F., 34.\\nForce, magnetizing, 22.\\nmagnetomotive, 20, 26, 245.\\nunits of, 1.\\nFoot-pound, 1.\\nFrequency of commutation, 84.\\nFriction of bearings, 89.\\nof brushes, 60.\\nFuses, 10.\\nGap, air, 69, 81, 85, 233.\\nGenerators [see dynamo], 31.\\nHeat of current, 9.\\nHeating of armatures, 39.\\nHolders for brushes, 61.\\nHysteresis, 27.\\nHysteresis\\nlosses by, 89.\\nInductance, 17, 18, 84.\\nInduction\\nelectro-magnetic, 13.\\nmutual, 18.\\nself, 17, 79.\\nInductors, 34, 45.\\nInput, 92.\\nIntensity of magnetic field, 1 2.\\nJig, for filing brushes, 62.\\nJoints in magnetic circuit, 76.\\nJoule, definition of, 1.\\nLag, 82.\\nof brushes in a motor, 165.\\nLamination, 38.\\nLaw of Steinmetz, 29.\\nLead, 82.\\nLeakage, magnetic, 73.\\ndetermination of, 260.\\nin compound motor, 175.\\nLength of armature, 237.\\nof active conductor, 235.\\nLines of force, 12.\\nLink, fuse, 10.\\nLosses, 92, 93.\\narmature, 238.\\ncommutator, 59.\\nfixed, 167.\\nI 2 R, 9.\\nin operation, 89.\\nvariable, 167.\\nLubrication, 65.\\nMagnet, field, 35, 69.\\nMagnets, 70, 96.\\nMaterials, insulating, 6.\\nmagnetic, 24, 68.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0291.jp2"}, "292": {"fulltext": "28o\\nINDEX.\\nMatthiessen, standard of, 6.\\nMeasurement of temperature rise, 42.\\nMelting of commutator bars, 83.\\nMeters, recording watt-hour, 182.\\nMica, 7, 59.\\nMil, circular, 6.\\n-foot, 6.\\nMotor, brake, 179.\\ncompound wound, 174.\\ncounter E. M. F. of, 163.\\ndirection of rotation of, 161.\\nfor railways, 187.\\nfor automobiles, 200.\\nfor mills, 203.\\nprinciple of, 161.\\nrated, 274.\\nseries, 185.\\nMotor-generators, 215.\\nOilers, 65.\\nOperation, care in, 225.\\nOutput, 92.\\nOver-compounding, in.\\ncoils for, 246.\\nPermeability, 22.\\nPermeameter, 253.\\nPermeance, 25.\\nPlane\\ncommutating, 78.\\nneutral, 78.\\nPoint, running on controller, 197\\nPole, magnetic, 12.\\nPole pieces, 67, 75.\\nPotential, magnetic, 19.\\nPower, lines of, 99.\\nof electric current, 8.\\nunit of, 2.\\nPressure, 4.\\nPrevention of sparking, 85.\\nProcess of commutation, 77.\\nRating of machines, 39.\\nReaction of dynamo armature, 80.\\nof dynamotor armature, 208.\\nof motor armature, 165.\\nRectifier, compounding, 112.\\nRe-entrancy, 46.\\nRegulation, arc dynamo, 132.\\nhand, 104.\\nself, 1 10- 1 13.\\n(see speed).\\nReluctance, 25.\\nof dynamo-magnetic circuit, 242.\\nReluctivity, 26.\\nReport of Standardization Commit-\\ntee of the American Insti-\\ntute of Electrical Engineers\\non efficiency, 92.\\non regulation, 116.\\non spark-gap voltages, 266,\\non temperature elevation, 40.\\non testing dielectric strength,\\n270.\\nResistance, armature, 240.\\nbrush contact, 60, 90.\\nmeasurement of, 263.\\nResistivity, 5.\\nRetentivity, 28.\\nRheostats, Carpenter enamel, 108.\\noverload, 172.\\npacked card, 105.\\nstarting, 169.\\nWard Leonard Electric Co.,\\n108.\\nWirt, no.\\nRise of temperature, 41, 91, 60.\\nRockers, 61, 64.\\nRule, Fleming s, 16.\\nSaturation of teeth, 85.\\nShafts, 64.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0292.jp2"}, "293": {"fulltext": "INDEX.\\n28l\\nShape of pole pieces, 86,\\nSheet, data for design, 247.\\nShell, magnetic, 20, 21.\\nShifting of brushes, 85.\\nShoe, pole, 75.\\nShort-circuit of armature coil, 226.\\nSkewing of field, 81.\\nSlip-rings, 31.\\nSlotting of poles, 86.\\nSolenoid, 21.\\nbrake, 180.\\nSpan, polar, 69.\\nSpark, voltage of, 266.\\nSparking, 61, 83, 85, 225,\\nSpectrum, magnetic, 13.\\nSpeed, armature, 239.\\nmotor, 163.\\nslow, 178.\\nhand regulation of, 175.\\nLeonard system of regulation,\\n176.\\nseries resistance regulation, 176.\\nSteinmetz, law of, 29.\\nStrength, test of dielectric, 264.\\nSurface, for radiation in armature,\\n240.\\nTeazer for Bullock system of speed\\ncontrol, 209.\\nTeeth, 85.\\nTemperature, critical, 25.\\nmeasurement of, 42.\\nrise of, 41, 43, 60, 91.\\nTension of brush springs, 62.\\nTheory of self-regulation of dyna-\\nmos, 113.\\nTorque, 2.\\nTransformer for high potentials, 266.\\nTurns, series, no.\\nUnit, absolute and practical, 2.\\nmechanical, 1.\\nof current, 3.\\nof potential difference, 3.\\nof resistance, 3.\\npole, 12.\\nVelocity, peripheral of armature, 234.\\nVentilation, ducts for, 39.\\nVulcabeston, 7.\\nWatt, definition of, 2.\\nWheatstone s bridge, 263.\\nWindage, 89.\\nWinding chord, 52.\\nclosed-coil, 45.\\ncross-connected, 48.\\ndrum, 51.\\nopen-coil, 44.\\nring, 47.\\nseries, 70, 97.\\nshort-connection, 49.\\nshunt, 70, 97.\\nWires, binding, 55.\\nWork, 1, 9, 19.\\nYoke, 36, 67.", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0293.jp2"}, "294": {"fulltext": "", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0294.jp2"}, "295": {"fulltext": "LIST OF WORKS\\nON\\nElectrical Science\\nPUBLISHED AND FOR SALE BY\\nD. VAN NOSTRAND COMPANY,\\n23 Murray 27 Warren Street,\\nNEW YORK.\\nATKINSON, PHILIP. Elements of Static Electricity, with full de-\\nscription of the Holtz and Topler Machines, and their mode of operating.\\nIllustrated. 12mo, cloth $1.50\\nThe Elements of Dynamic Electricity and Magnetism. 12mo, cloth. $2.00\\nElements of Electric Lighting, including Electric Generation, Measure-\\nment, Storage, and Distribution. Ninth edition, fullv revised and new matter\\nadded. Illustrated. 8vo, cloth $1.50\\nPower Transmitted by Electricity and applied by the Electric Motor, including\\nElectric Eailway Construction. Third edition, fully revised and new matter\\nadded. Illustrated. 12mo, cloth $2.00\\nBADT, F, B. Dynamo Tender s Hand-book. 70 Illustrations. 16mo,\\ncloth $1.00\\nElectric Transmission Hand book. Illustrations and Tables. 16mo,\\ncloth $1.00\\nIncandescent Wiring Hand-book. Illustrations aud Tables. 12mo, cloth.\\n$1.00\\nBell Hanger s Hand-book. Illustrated. 12mo, cloth $1 .00\\nBIGGS, C. H. W. First Principles of Electricity and Magnetism. A book\\nfor beginners in practical work. With about 350 diagrams and illustrations.\\nIllustrated. 12mo, cloth ..$2 00\\nBli AKESLE Y, T. H. Papers on Alternating Currents of Electricity, for\\nthe Use of Students and Engineers. Third edition, enlarged. 12mo, cloth.\\n$1.50", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0295.jp2"}, "296": {"fulltext": "E\u00c2\u00bbOTTONE, S. R. Electrical Instrument-making for Amateurs. A Prac\\ntical Hand-book. Sixth edition. Enlarged by a chapter on The Tele-\\nphone. With 48 Illustrations. 12mo, cloth $0.50\\nElectric Bells, and all about them. A Practical Book for Practical Men.\\nWith over 100 Illustrations. 12mo, cloth $0.50\\nThe Dynamo How Made and How Used. A Book for Amateurs. Sixth\\nedition. 100 Illustrations. 12mo, cloth., $1.00\\nElectro-motors How Made and How Used. A Hand-book for Amateurs\\nand Practical Men. Illustrated. 12mo, eloth $0.50\\nRUBIER, E. T. Questions and Answers about Electricity. A First Book for\\nBeginners. 12mo, cloth $0.50\\nCARTER, E. T. Motive Power and Gearing for Electrical Machinery; a\\ntreatise on the theory and practice of the mechanical equipment of power\\nstations for electric supply and for electric traction. Illustrated. 8vo,\\ncloth $5.00\\nCROCKER, F. B., and S. S. WHEELER, The Practical Management of\\nDynamos and Motors. Illustrated. 12mo, cloth 31.0c\\nCROCKER. F. B. Electric Lighting. Volume I., The Generating Plant.\\n8vo, cloth. Illustrated $3.00\\nDESMOND, CHAS. Electricity for Engineers. Part I. Constant Cur-\\nrent. Part II. Alternate Current. Revised edition. Illustratedo 12mo,\\ncloth $2.50\\nDU MONCEL, Count TH. Electro-magnets The Determination of the\\nElements of their Construction. 16mo, cloth. (No. 64 Van Nostrand s\\nScience Series.) $0.50\\nDYNAMIC ELECTRICITY. Its Modern Use and Measurement, chiefly\\nin its application to Electric Lighting and Telegraphy, including 1. Some\\nPoints in Electric Lighting, by Dr. John Hopkinson. 2. On the Treatment\\nof Electricity for Commercial Purposes, by J. N. Schoolbred. 3. Electric\\nLight Arithmetic, by R. E. Day, M. E. 18mo, boards. (No. 71 Van Nos-\\ntrand s Science Series.) $0.50\\nEWING9 J** A. Magnetic Induction in Iron and other Metals. Second\\nissue. Illustrated. 8vo, cloth $4.00\\nFLEMING, Prof. A. J. The Alternate-Current Transformer in Theory\\nand Practice. Vol. I. The Induction of Electric Currents. 500 pp. New\\nedition. Illustrated. 8vo, cloth $5.00\\nVol. II. The Utilization of Induced Currents. 594 pp. Illustrated. 8vo,\\ncloth $5.00\\nFOSTER, HORATIO A. (with the collaboration of eminent specialists), Elec-\\ntrical Engineers Pocket-book. Illustrated with many cuts and diagrams.\\nPocket size, limp leather with flap. (In Press.)\\nGORDON, J. E. H. School Electricity. 12mo, cloth $2.00\\nGORE, Dr. GEORGE. The Art of Electrolytic Separation of Metals\\n(Theoretical and Practical). Illustrated. 8vo. cloth $3.50", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0296.jp2"}, "297": {"fulltext": "RASKINS, C. H. The Galvanometer and its Uses. A Manual for Elec\u00c2\u00ab\\ntricians and Students. Fourth edition, revised. 12mo, morocco $1.50\\nTransformers Their Theory, Construction, and Application Simplified.\\nIllustrated. 12mo, cloth $1.25\\nHAWKINS, C. M.A., A.I.E.E., and WAIiMS, F., A.I.E.E.\\nThe Dynamo, its Theory, Design, and Manufacture. 190 Illustrations\\n8vo, cloth $3.00\\nHOBBS, W. R. P. The Arithmetic of Electrical Measurements. With\\nnumerous examples, fully worked. New edition. 12mo, cloth $0.50\\nHOSPITALIER, E, Polyphased Alternating Currents. Illustrated. 8vo,\\nCloth $1.40\\nINDUCTION COILS How Made and How Used. Fifth edition. 16mo,\\ncloth. 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The Electrical Engineer s Pocket-book Modern Rules,\\nFormulae, Tables, and Data. 32mo, leather $1.75\\nKENNELLY, A, E\u00c2\u00ab Theoretical Elements of Electro-dynamic Machinery.\\nVol. I. Illustrated. 8vo, cloth $1.50\\nKILGOUR, M. H., and SWA\u00c2\u00a3, H., and BIGGS, C. H. W. Electri-\\ncal Distribution Its Theory and Practice. Illustrated. 8vo, cloth. .$4.00\\nLOCK WOOD, T. I Electricity, Magnetism, and Electro-telegraphy.\\nA Practical Guide and Hand-book of General Information for Electrical\\nStudents, Operators, and Inspectors. Revised edition. 8vo, cloth. Pro-\\nfusely Illustrated $2.50\\nLODGE, PROF. OLIVER J. Signalling Across Space Without Wires:\\nbeing a description of Hertz and his successors. Third edition. Illustrated.\\n8vo, cloth 2 00\\nLORING, A. E. A hand-book of the Electro-magnetic Telegraph. 16mo,\\ncloth. (No. 39 Van Nostrand s Science Series.) 50\\nHORROW, J. T., and REID, T. Arithmetic of Magnetism and Electricity.\\n12mo, cloth.. s1 00", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0297.jp2"}, "298": {"fulltext": "1TEUNRO, JOHN, C.E., and JAMIESON, ANDREW, C.fi. A\\nPocket-book of Electrical Rules and Tables, for the use of Electricians and\\nEngineers. Thirteenth edition, revised and enlarged. With numerous diagrams.\\nPocket size, leather $2.50\\nNIPHER, FRANCIS E., A. M. Theory of Magnetic Measurements, with an\\nAppendix on the Method of Least Squares. 12mo, cloth $1.00\\nOHM, Dr. G. S. The Galvanie Circuit Investigated Mathematically. Berlin\\n1827. Translated by William Francis. With Preface and Notes by the Edi-\\ntor, Thos. D. Lockwood. 12mo, cloth. (No. 102 Van Nostrand s Science Se-\\nries) $0.50\\nOUDIN, MAURICE A. Standard Polyphase Apparatus and Systems, contain-\\ning numerous photo-reproductions, diagrams and tables. Second edition,\\nrevised. 8vo, cloth illustrations $3.00\\nPLANTE, GASTON. The Storage of Electrical Energy, and Researches\\nin the Effects cieated by Currents combining Quantity with High Tension.\\nTranslated from the French by Paul B. ElweL. 89 Illustrations. 8vo $4.00\\nPOPE, F. L. Modern Practice of the Electric Telegraph. A Hand-book for\\nElectricians and Operators. An entirely new work, revised and enlarged,\\nand brought up to date throughout. Illustrations. 8vo, cloth $1 .50\\nPOOLE, J. The Practical Telephone Hand-book. Illustrated. 8vo, cloth.\\n$1.50\\nPREECE, W. M., and STUBBS, A. J. Manual of Telephon Illus-\\ntrated. 12mo, cloth $4.50\\nRECKENZAUN, A. Electric Traction. Illustrated, 8vo 9 cloth $4.00\\nRUSSELL, STUART A, Electric-light Cables and the Distribution of\\nElectricity. 107 Illustrations. 8vo, cloth $2.25\\nSALOMONS, Sir DAVID, M.A. Electric-light Installations. Vol. I.\\nManagement of Accumulators. A Practical Hand-book. Eighth edition\\nrevised and enlarged. 12mo, cloth. Illustrated o $1.50\\nVol. II. Apparatus $2.25\\n-Vol. III.: Application $1.50.\\nSCHELLEN. Dr. H. Magneto-electric and Dynamo-elaetric Machines:\\nTheir Construction and Practical Application to Electric Lighting and the\\nTransmission of Power. Translated from the third German edition by N.\\nS. Keith and Percy Neymann, Ph.D. With very large Additions and Notes\\nrelating to American Machines, by N. S. Keith. Vol. I., with 353 Illustra-\\ntions. Second edition $5.00\\nSLOANE, Prof. T. O CONOR. Standard Electrical Dictionary. 300\\nIllustrations. 8vo, cloth o....$3.00\\nTHOM, C, and JONES, W. H. Telegraphic Connections, embracing\\nrecent methods in Quadruplex Telegraphy,, 8vo, cloth. Twenty colored\\nplates........... .....$1.50", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0298.jp2"}, "299": {"fulltext": "THOMPSON, EDWARD How to Make Inventions; or, Inventing as\\na Science ana an Art. An Inventor s Guide. Illustrated. 8vo, paper..$1.00\\nTHOMPSON, Prof. S. P. Dynamo-electric Machinery. With an Intro-\\nduction and Notes by Frank L. Pope and H. R. Butler. Fully Illustrated.\\n(No. 66 Van Nostrand s Science Series.) $o.5C\\nRecent Progress in Dynamo-electric Machines. Being a Supplement to\\nDynamo-electric Machinery. Illustrated. 12mo, cloth. (No. 75 Van\\nNostrand s Science Series.).. $0.50\\nThe Electro-magnet and Electro-magnetic Mechanism. 213 Illustrations.\\n8vo, cloth ...$6.00\\nTREVERT, E. Practical Directions for Armature and Field-magnet\\nWinding, 12mo, cloth. Illustrated $1.50\\nTUMLIRZ, Dr. Potential, and its application to the explanation of Elec-\\ntrical Phenomena. Translated by D. Robertson, M.D. 12mo, cloth. .$1.25\\nTUNZELUIANN, G. W. de. Electricity in Modern Life. Illustrated.\\n12mo, cloth $1 25\\nURQUHART, J W. Dynamo Construction. A Practical Hand-book for\\nthe Use of Engineer Constructors and Electricians in Charge. Illustrated.\\n12mo, cloth $3.00\\nWALKER, FREDERICK. Practical Dynamo-building for Amateurs.\\nHow to Wind for any Output. Illustrated. 16mo, cloth. (No. 98 Van Nos-\\nstrand s Science Series.) $0.50\\nWALKER, SYDNEY F. Electricity in our Homes and Workshops. A\\nPractical Treatise on Auxiliary Electrical Apparatus. Illustrated. 12mo,\\ncloth $2.00\\nWEBB, H. Ii. A Practical Guide to the Testing of Insulated Wires and\\nCables. Illustrated. 12mo, cloth ....$1.00\\nWEYMOUTH, F. MARTEN. Drum Armatures and Commutators.\\n(Theory and Practice.) A complete treatise on the theory and construction\\nof drum-winding, and of commutators for closed-coil armatures, together\\nwith a full resume of some of the principal points involved in their design;\\nand an exposition of armature reactions and sparking. 8vo, cloth. Illus-\\ntrated... $3.00\\nWORMELEi, R. Electricity in the Service of Man. A Popular and Prac-\\ntical Treatise on the Application of Electricity in Modern Life. From the\\nGerman, and edited, with copious additions, by R. Wormell, and an Intro-\\nduction by Professor J. Perry. With nearly 850 Illustrations. Royal 8vo,\\ncloth $3.00\\nA General Catalogue -SO pages\u00e2\u0080\u0094 of Works in all branches\\nof Electrical Science furnished gratis on application*", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0299.jp2"}, "300": {"fulltext": "U619\\nkJ", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0300.jp2"}, "301": {"fulltext": "", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0301.jp2"}, "302": {"fulltext": "", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0302.jp2"}, "303": {"fulltext": "", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0303.jp2"}, "304": {"fulltext": "", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0304.jp2"}, "305": {"fulltext": "", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0305.jp2"}, "306": {"fulltext": "", "height": "4561", "width": "2742", "jp2-path": "dynamoelectricma01shel_0306.jp2"}}